Impressive collection!
I've bought a few, but my main problem is lack of space and no place to really display them since I tend to gravitate towards the larger models. I tend to focus more on statues/figures of actresses, because they're almost impossible to find. And it has to actually LOOK like the actress (I passed on the Lynda Carter Wonder Woman statue because it looked nothing like her).
My latest major acquisition was a 12-inch Black Widow done as an almost photo-real representation of Scarlet Johannson.
http://ironmanfan.blogspot.com/2010/05/16-black-widow-limited-edition.html
(Same company put out a Scarlett-as-Silken Floss from The Spirit that was equally photo-real, but I never got it and I'm kicking myself as it's impossible to obtain now. They have a nice one of Jessica Biel from Blade Trinity I'm considering.)
My favorite is an 18-inch figure of The Bride from Kill Bill - Uma Thurman, ahoy. My rarest is a Lara Croft figure that is in the likeness of Angelina Jolie. My weirdest - someone gave me a 12-inch Donald Trump "action figure" a few years ago. It's actually really well done.
(I was planning on adding links to images of the first two, but I couldn't find any suitable ones on Google that didn't lead to either auction sites or weird webpages from overseas. Guess that shows how rare they are!)
Superheroes-wise, I confess I go for the cheesecake a bit. I have the DC Covergirls Power Girl, as well as the bigger "action figure" version (also the smaller one visible in the Flicker pictures above). I also picked up the DC Animated version of Wonder Woman. I've also got a growing collection of Doctor Who action figures (including a 10-inch Tenth Doctor that I'm told is pretty uncommon in North America). I figured, if my mom could spend her 50s collecting Cabbage Patch Dolls, I can spend my 40s collecting action figures. Same difference as stamps, really (that rare Jolie figure will probably appreciate in value just as much!

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Alex