Well here are my choices based on what i have in my small collection so i narrowed it down to 4
4th. Movie 1 Deluxe Dropkick This one is really good for 1 main reason, His car is great but when you look at him from a distance and realize he looks even better than you average army building bot
since he is wielding a Decepticon logo across his whole car which is amazingly detailed. Add in the fact he is is simple to transform by unfolding the legs, twist out the chicken legs and unfold the arms from the front end and you have a solid combo.
3rd. Cybertron Downshift This easy guy has a excellent muscle car look, is easy and is loaded with options for bot mode.
2nd. Classics 2 Pack "The Ultimate Battle"2006 Deluxe Optimus Prime This guy has a simple transformation exactly like G1. Although he seems downscaled quite a bit for a deluxe size figure, dont let him fool you he's actually quite good and worth the price.
1st. Voyager Cybertron Defense Scattorshot This guy is dead simple, undo the legs plates, rotate the leg assembly, pull the arms to the side and reveal the robot moded fists and feet. In both modes this guy is loaded for bear with a ton of armaments and more than enough to be a one man army. I mean 22 mini rockets, a big rifle + additional cyber key cannon and a dual barrel extra missiles
It's enough to make all but the bravest and strongest Decepticons flee for their lives
That is why he is my number 1 choice, i can transform this guy blindfolded, he is that simple