If you are planning to buying new fitness equipment, I recommend you to shop well and to consider at least some of the following manufacturers: Cybex, Hammer Strength, Life Fitness, Gervasport, Body-Solid, Icarian-Precor, Hoist, Gym 80, Paramount, Nautilus, WNQ, Maxicam, Apex, Yukon, Legend, Magnum, Maximus, Pro Fitness, MedX, Atlantis, Powertec, Star Trac, Wilder, Power Strength, Body Masters, FreeMotion, Strive, Flex, Matrix, Barbarian Line, Inter Atletika, BH HiPower, Sport-Thieme, ZhengZhou Sanhui, Impulse Fitness, Yeekang Fitness, L+K, Panatta Sport, Teca Fitness, Pulse Fitness, Multi Form, Bcube, Teuwsen Sportgeraete, Kaesun, Exe Fitness, MF Sport, Iron Grip, Hampton, Ivanko, Cemco, Troy, Intek, TuffStuff, Quantum, Nebula, Power Lift, ProSpot, BodyCraft, GP Industries, Sorinex, Bomb Proof, TechnoGym. (If I miss any important brand, please let me know.) Never buy a new weight machine without testing it. 

Weight Machine Selection Criteria 
When you are choosing a good weight machine to do your muscle building exercises, you should make sure that it passes the following criteria: 
I strongly advise to stick to the basic machines. Use the same type of machines that the champions have been using for decades, and are still using today. The best weight machines have a simple construction. The more complex and trendy a machine is designed, the less effective it usually is in stimulating muscle growth. 

The best weight machines provide a very natural body movement throughout the full range of motion. The machine must be constructed in such a way and the hand grips must be located in such places that your body is always in a comfortable position/posture, which allows you to generate maximum power during heavy reps. 

A good weight machine must have a strong, robust, and stable construction made from solid steel. You do not want to use or own a machine that cannot survive a single workout of Ronnie Coleman. The best machines can easily survive a century of heavy duty workouts. 
A good weight machine must be adjustable to the length and body construction of all its users. Everybody between 5 and 7 feet (150 - 210 cm) tall should be able to use it under optimal conditions. 
A good weight machine must allow the exercise to be performed over the greatest possible range of motion, with a complete stretch of the muscle at the bottom of the rep and full contraction at the top of the rep. By nature, machines usually provide a smaller range of motion compared to free weights. It becomes even worse when the machine is designed badly, forcing the user into a restricted range of motion, that totally erases the effectiveness of the exercise. 

A good weight machine must keep the muscle under continuous tension with a constant force throughout the full repetition, from the bottom till the top of the movement. Unfortunately, many machines have a significant mechanical friction that lowers the tension on the muscle during the down-phase of the reps. This mechanical friction is usually higher for stack machines (using cables running over pulleys or wheels) than for plate loaded machines (using standard barbell plates). Plate loaded machines, on the other hand, have the disadvantage that the force does not remain 100% constant throughout the movement as the weights make a rotation in an arch around a hinge point. It is not always clear which is better, plate loaded or cable machines, it really depends on the exercise and the design of the machine. Avoid machines with a high mechanical friction. 

Recommended Equipment 
Let's take a look now, at the equipment that we need to do the recommended exercises, and discuss some of its most critical aspects. Pictures and movies of the equipment can also be found at bodybuilding.com or in my imaginary dream gym. 
Chest 
For the chest exercises you need dumbbells, an Olympic bar, Olympic plates and Olympic collars, a flat-incline-decline bench, and a smith machine. The smith machine must be vertical (not angled), must allow the bar to slide from the floor up to about 8 feet (2.5 m) high, and must be very heavy and stable so that it doesn't slip away when it is used for heavy squats. 
The dumbbells are without any doubt the most important equipment in any gym. Dumbbells must lay stable in the hands. Therefore, it is recommended to choose dumbbells of standard shape, size and grip, rather than any fancy looking new design. A gym must minimally have a pair of dumbbells of 2, 3, 4, 5,..., 19, 20 kg, increasing in steps of 1 kg (2.2 lbs), and 22, 24, 26, 28 ,..., 48, 50 kg increasing is steps of 2 kg. 
A good flat-incline-decline bench must be very stable, not too wide so that the shoulders have enough freedom to move during dumbbell presses, not too high so that the heels of both feet can be placed on the floor, and adjustable to the following angles: -22°, 0°, +22°, +45°, +67°, and +90°. Unfortunately, many adjustable benches don't allow to go decline (-22°). 
People who like to do heavy bench presses may prefer separate bench press setups for flat, incline and decline bench presses. 
Although I don't recommend you to do cable crossovers for your pecs, the cable crossover machine is a very all-round cable machine that can be used for many exercises (biceps, triceps, shoulders etc.). Therefore I do believe that every gym should have one. It is very important that the pulleys can be adjusted in height from the floor level up to more than 2 meters (7 feet). 
Abdominals 
For the full range of motion crunches a very steep decline (-50°) bench with leg support is needed, which can also be used to do the lying leg raises, if set in a less steep angle (-22°). For the hanging leg raises, a vertical leg raise construction is needed. 
Forearms 
All you need for the forearm exercises is some dumbbells, straight barbells, and a flat bench or preacher bench to support your arms. 
Shoulders 
All you need for the deltoid exercises is dumbbells, and a smith machine. 
Upper trapezius 
Dumbbells are all you need. 
Triceps 
For your triceps exercises you need dumbbells, an EZ-bar with plates and collars, a flat-incline-decline bench, parallel dip bars, and a cable column with EZ-grip. I prefer to use EZ-bars for all my arm exercises because they allow a much more natural grip for the wrists, which provides extra strength during the exercise and keeps the wrists free from injuries. 
Upper and middle back 
To do the exercises for your upper back (lats) you absolutely need a cable lat pulldown machine with a wide-grip bar, a middle-grip bar (palms facing each other), and a small-grip V-bar. A plate loaded lat pulldown machine is also very effective. For both pulldown machines it is very important that the distance between the seat and the grips is large enough so that even a very tall person can fully extend his arms, and get a full stretch of his lats, at the bottom of the repetition. Therefore, it is best if the seat is adjustable in height. 
It is also very handy to have a chin-dip-ab combination with a high pull-up bar for chins, two parallel dip bars, and an arm/back support for hanging leg raises. 
For the middle back exercises a seated row machine and a lying T-row machine are must-haves. I have experienced very good plate loaded as well as stack loaded seated row machines. Most important is that the position of the chest pad must be adjustable so that all people (short or long arms) can easily grab the grips, and are able to enjoy a full range of motion with fully extended arms and completely stretched muscles at the bottom of the movement. The lying T-row machine must be plate loaded, and preferably have various grips (wide, middle, narrow) and an in height adjustable feet plate. Seated cable row columns are also very popular, but in my opinion less essential for building muscle mass than the seated row machine and lying T-row machine. 
Biceps 
For your biceps exercises you need dumbbells, an EZ-bar with plates and collars, an incline bench, and a preacher bench. The preacher bench must be adjustable in height. 
Hamstrings 
Lying leg curl, seated leg curl, and standing leg curl machines are usually stack loaded cable machines. It is very important that they allow the greatest possible range of motion, and that the pad at the back of your lower leg can be adjusted in height. For the standing leg curl machine, the location of the hand grips is very important, as they contribute a lot to the stability of your body during heavy leg curls. The bent-legs hyperextensions are done at the same hyperextension machine as used for the lower back (see below). 
Lower back 
A hyperextension machine can be horizontal or 45° inclining. Horizontal hyperextension machines put much more stress on the knees. The stress on the knees is lower if the pads that support the back of the legs are not too close to the feet. If the pad supporting the pelvic does not have a shape that provides enough space for your testicles, performing hyperextensions can be very uncomfortable. 
Calves 
A standing calf raise machine must be a vertical machine, can be stack or plate loaded, and must be very strong, robust, and stable because some guys use very heavy weights for this exercise. I have used very good plate loaded as well as stack loaded seated calf raise machines. 
Quadriceps 
While the barbell squat is the king of all bodybuilding exercises, the hack squat machine is without doubt the king of all weight machines. Every self-respecting gym must have a hack squat, as it is the best quadriceps building exercise that exists. No other squat or leg press machines can replace the hack squat. The best hack squats have an angle of about 45° and must be plate loaded. The feet plate must be big enough (about 80 x 80 cm), have a rough surface against slipping, and preferably have an adjustable angle. The success of the hack squat is its simplicity. 
For the barbell squat and the front squat you need a barbell, a smith machine, a squat rack or power cage, and a wooden plank of about 2 inches thick (e.g. 5 x 20 x 80 cm) for under the heels. A good power cage has in height adjustable parallel bars at the sides that can catch the barbell is case you would fall. 
For power movements every gym also needs to have a leg press machine. A good leg press machine must be plate loaded, with the seat near the floor, and the weights sliding under an angle of about 45°. The angle of the back of the seat is preferably adjustable. A leg press machine must be extremely strong and robust because the biggest guys can press up to 2,000 lbs (1000 kg) of weights. 
None of the plate loaded leg extension machines that I have tried so far were really good. Therefore I think that a leg extension machine is best a stack loaded cable machine. The best leg extension machines have a seat that declines slightly backwards. I never use leg extension machines that do not allow me to lower the weight 100% (to full quadriceps stretch) without losing the tension on the muscle at the bottom of the rep. 
A sissy squat is a very simple construction that should have 2 long parallel bars pointing backward, so that you can comfortably lean completely backwards during your squats without falling down. 
Inner and outer thighs 
Thigh adductor and thigh abductor machines must be stack loaded cable machines that allow full range of motion.
.....Back