As a kid, the Incredible Hulk was my favourite super hero. Hulk is big, green and means business.
The very first action figure I got for Isaac was actually Hulk (the one of the right). He is from the last Hulk film starring Edward Norton. By pressing a button on his back, he lights up. The Abomination, on its left, was the second action figure Isaac got.
From all the ones below, I have to say that Red Hulk is my favourite. Absorb Man is very nice, so is Skaar and Samson.