Loving all the headcanon and fic recs so far (in fact the only fics I can think to rec at the moment have already happened, curses!).

I love Natasha & Steve and Natasha & Thor friendship fics. I can see her getting along so well with them. For Clint, we didn't really see enough of him so I'm less clear on my headcanon for movieverse. I think he and Steve would get along well, and he'd have a surprisingly close bond with Bruce (because of the reasons mentioned above, knowing what it's like to have something control your body).

My deepest held headcanon at the moment is that Natasha has much more of a bond with Fury than with Coulson. Nat and Fury bond over being occasionally amoral spies, and he sees her as almost a daughter.