For cardio, IMax or MIC (I think MIC is a tad tougher, but either is hell). After that, IMax2 and then Imax Extreme.
For weights, PUB and PS Legs. If you choose your weights in an optimally cruel way, Slow and Heavy is pretty tough for upper body, but I don't have the poundage to challenge my legs enough. Leaner Legs is very very tough. PLB also. Among these, it's hard to choose.