-Why Clint grabs a bow when Coulson says he needs "eyes up high with a gun"
-Fics with Clint disliking rainy weather for whatever reason
-Tony highly protective of his AIs (Dummy especially)
-Tony quietly doing repairs on things to protect 'his' people (I read one in which he does constant maintenance on Steve's bike, because that's how he expresses his affection. Rhodey says something along the lines of "That bike will never, ever fail you. Never. It's the best protection he can offer."
-Clint with hawk-like behaviors
-Coulson getting pissy that Iron Man and Thor kept ducking debriefing in their respective movies
I'm thrilled with any length, any genre but horror, and as far as pairings go, I tend to adore Steve/Tony and Clint/Coulson (with or without Natasha), but only really get squicky when Banner is paired up with Barton or Coulson. Gen (no pairings) is always welcomed too, as well as any ratings. Even if the scene is just a small part of a bigger story, I'll still be thrilled.
(And of course, I'm always, always looking for any hurt!Tony, hurt!Coulson, hurt!Clint, and deaf!Clint... *sheepish)