Loki
Super Freak
I don't think Nolan's take on the Avengers would fly very well. TA is suppose to be light and fun filled not broody and dark.
This makes me wonder how TA could turn out under Nolan's direction though, regardless of what it's supposed to be considering the comics and genre it's from.
He has a way of turning non-believable elements into something workable (the Bat, Bane's mask to some extent). The Hulk is right under that category, and Loki and the magical elements could be more of a scientific thing, given that magic is (sorry, gonna quote something from the movie Thor here), "just science that we don't understand yet".
Sure, the atmosphere would be different, but I'd go see it!