Only five choices? It was hard to whittle down.
Vector Prime is probably tops for me out of the line. Give it a waist joint and it's another one of those "I don't know how else this could really be improved" kind of toys. The Takara deco is gorgeous to look at, but I definitely appreciate the Hasbro take on it as well. The Universe 2.0 "Last Autobot" version is also a big home run.
Leader Megatron is an all time great in the entire Transformers line, imo. Three fun modes and outside of some ankle rockers and unfortunate safety-plastic, it's hard to find a flaw.
I also voted for Menasor because you people don't know a good thing when it stares at you in the face with its glorious drill and dumb alt mode and super cool Mini-con that stops just short of homaging freaking Victory's Brainmasters