Well, I'm just a n00b
but I'll play along, and post what seems to work best for me, so far...
Legs: Low bar squat, if I have to pick just one for quads *and* hams, etc.
Chest: Dumbbell bench, without a doubt. But (flat) barbell is second best.
Back: Just one? Jesus. Um... barbell rows.
Calves: I don't bother
, but I guess standing calf raises would be best...
Shoulders: BTN press or just plain old overhead press. Or both
.
Biceps: Barbell curl.
Triceps: Dips.
Traps: Conventional deadlift (because I had to pick just one for "back".)
Forearms: Wrist roller, actually.
Hey, like I said, seems to work for me.
Abs: Situps, on a decline bench, with weight.
Most of that stuff, I still do (plus some). The rest, I've tried for a while at least.