First, apologies if any of these choices bleed back into 2012. Second, I focused on in-scale items and those based around the core of my hobby. Otherwise, I do agree with Redclaw's Boba Fett (and Han Solo for that point) as being arguably at the top of the list from a toy-only perspective.
1. Prof. X. Not only for all the reasons pluv rattled off, but also because with just a few mods, that head becomes pretty versatile.
2. Avengers Assemble Iron Man (the articulated version). I've written about this one before. It takes some mods to put him on par with other versions, artic.-wise. But feels most like Stark in a suit of armor than any prior incarnation.
3. I'll echo the Tony Stark figure currently for sale (though I think I might have first got a cast copy of it prior to 2013, I can't recall?). If I had not already made a custom I was happy with, I'd be all over the current production version.
4. MU Elektra - It's not a character I'm that into, but for customizing, especially for someone who enjoys making female customs - it's a great fodder figure, wonky proportions and all.
5. Avengers Assemble Black Widow. If you prefer your figs straight out of the box, this could well be a definitive comic styled BW. For me, the accessories and the limbs (mostly) make for solid custom parts, just as the movie version did. But the head is the real prize here. I used one for a Vicky Vale, but have seen it as Cover Girl and others. Lots of potential.
6. Not-Kwinn. I have to agree again. Great figure, just not as Kwinn. I'm using these up all over the place, for my AT themed settings. And I'm also starting to parts swap, to give some versions pants, or to put the shorts onto a Sgt. Stone and have a different colored shirt, etc... Just a fun figure all around.
Just Not as Kwinn.7. I don't disagree with pluv's Roadblock selection. It is a great figure. And I'm using the one I got for a custom. It's lower on my list mainly because I have been torn on how to use it. I ended up directing it towards a RnR custom. It just didn't feel like Roadblock to me, so I didn't use it as the base for that...and though the authentic Rock tat is sweet, I don't really have a place for the Rock as the Rock... I'm still perplexed. But I dig the figure.
8. DG Shipwreck - again I can't say for sure if he counts as 2013 or not. And I only have the blue sweater version. But it's great. An awesome starting point for a civilian or naval character, either one. I am keeping one as SW though, which is a rarity for me. I assume I'd find plenty of uses for the green version also, but haven't snagged one of those yet. The fact this was available at DG pricing was just gravy.
9. Dark Ninja - the closest I've come to army building a non-custom. I'm not even a ninja guy. but ever since Hypno posted his Joe Colton vs. the Black Dragons one-shot, I had to have some. It was like being punched in the face by the nostalgia of every Sunday morning action feature I ever saw as a kid.
10. Cobra Red Trooper (Ret. 3-pack). I don't want to army build him. I just have too many uses for those cool basic parts, molded in red. I have 2 but could stand a dozen more. HINT HINT
Honorable Metion: Firefly from the same Ret. 3-pack. This is what a classic update should look like and feel like. If I was more of a collector, it would be higher on my list. As is, he stands (along with a couple others from the list) as one of the few unmodified figures in my stash. And honestly, he's 10 times the toy that figures like Elektra are. But my customizing bend forces me to rank accordingly

EDIT: As I read through it again, I think Elektra would probably get bumped down to honorable mention status if I started over. And, I also agree with RC's Cobra Commander selection. I bought one to customize, but he's just too pretty as an iconic version of the character to chop up. Yet, since I'm not a huge CC fan, he'd not make my personal list.
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Kwinn_Lives wrote:
you have now won more JCAs than anyone in the history of the award.
Mysterious Stranger wrote:
You sir are the definition of a Renaissance Nerd... you do it all so damn well.