Prowl, either version. The original has superb pose ability and the ninja star hubcaps and the Samurai armor comes with a neat sidecar and the awesome samurai armor
It's incredibly difficult to choose any one toy, but I would have to consider Rodimus the best of the bunch, a product of all the engineering developments throughout the line. He's got an amazing vehicle mode, a very articulate and well-sculpted robot mode, and cartoon-accuracy all around. I would put Prowl, Ultra Magnus, and Cybertron Mode Optimus Prime as runners-up.
I have two (Well 4 if you count BB,who I hated and he broke,or Oil slick,who alas suffered the same fate as Universe Bluestreak of being given to me when I wasn't into TFs and were lost ) I would recommend Prowl(I have the samurai version)as cybertronian Prime's waist won't star together
The Animated portion of my collection is small (single digits!) so there's only a couple I have experience with. I echo the suggestions of Rodimus, and also want to add Cybertronian Ironhide and the voyager Seeker mold.
Choosing just one is really hard. I'm going to cheat and say Shockwave, Rodimus, or my personal favorite, Ironhide.
It's not a dumb question. I'm curous as well. Don't have any animated figures, but I like a few and I might get them sometime in the future. How's Arcee? Nobody recommended her and I think she neat.
I can't offer up just one. I have 6 floating around in my head right now so I'll give 3. Waspinator, Arcee and Blurr.
Blurr and Swindle are both VERY impressive deluxes. I know part of it is character bias, but they're deluxes that wildly exceeded my expectations. They ooze awesome, from their face sculpts to their articulation.
Sentinel Prime. Neat little transformation and unlike most of the line he has good plastic that can take some wear.