Use of 'intensity' should probably be clarified.
Russ, I'm assuming that by 'intensity' you mean % current 1RM, rather than perceived intensity à la HIT?
Personally, I think that the four variables in Russ' list are the most useful; all need to be manipulated to some degree depending on the goals of the trainee - even during the course of a cycle.
"Be the best that you can be."
Deadlift: 215kg (474lb) - pre-hernia!
Low-bar Back Squat: 190kg (419lb) 16/04/10 @BW ~210lb
Bench: 130kg (287lb) 01/02/13