Bodybuilders of old would use this form of training in the off-season, where they would train one (or at the most, two) exercises for each of their muscle groups. In general, most "old-timers" thought this was the best form of training for growing muscle, not to mention becoming bigger, stronger, thicker lifters. It wasn't until a couple of months from a contest that they would switch over to a multi-angular approach. They (rightfully, I might add) believed that multi-angular training splits were best done for "shaping" and "detailing" the muscles, but NOT for building big muscles in the first place.
Not only, however, is it good to limit the number of exercises performed for each bodypart, but it's also wise to limit the number of exercises per workout.
Enter the "Two Exercise Program."
This program is great for building muscle mass. If you used this program for the majority of the training for the rest of your life, then you would end up with a lifetime of great workouts, and plenty of good training experience.
Don't worry, there's also plenty of variety inherently built into this program.
First, I'm going to outline this program's parameters, then I'll give you an example of an actual training program. Here's the parameters:
1. Use only two exercises at each workout.
2. Pick exercises that use a lot of muscle groups at one time.
3. Use a (fairly) high amount of volume for each muscle group.
4. For the most part, alternate exercises from workout to workout.
5. For the most part, alternate set/rep ranges from workout to workout.
6. Train 3 days per week.
Here's what an example program (one week of training) might look like:
squats: 100 reps using the 2, 3, 5, 10 workout plan
dumbbell bench presses: 100 reps using the 2, 3, 5, 10 workout plan
snatch-grip deadlifts: 10 sets of 3 reps
barbell curls: 10 sets of 3 reps
dips: 5 sets of 5 reps
chins: 5 sets of 5 reps
Above all, have fun and be innovative with this program. It looks simple, but it's also highly rewarding.