MP-13 Soundwave is very good, and MP-8 Grimlock has a shiny gold chest (plus, he transforms into a freakin' T-Rex!).

But, if I had to show one figure to someone else to sum up why I like to collect transformers, it would have to be MP-10 Optimus. An iconic leader, great looking in both modes, and excellent posability (especially once I fixed his loose ankles). The trailer and extras are just gravy.