Universe: Any 
Prompt: Steve gets turned pre-serum state, being so frail that the avengers leave him home. Whoever did this to him had plans, and when Steve is alone in the Mansion/Tower he has to fend for himself. Home Alone action and Steve being creative on how to beat up the villain(s?) with little traps and toys.
Bonus Point: He gets caught in the end, after giving out some major damage to the bad guys and gets saved by the returning Avengers (Tony plz?). They are super impressed.

Universe: Any
Prompt: Tony and Steve can’t stand being around each other without verbally fighting, to the dismay of everybody, because the presence of the other makes them completely on edge (they are mates, but just dont get it!). When Tony is attacked, he finds out the hard way when Steve took the blow and is left unconscious for a long time.
Bonus Point: Tony tries to pin a still clueless Steve after he wakes up.

(Happy ending please!)  

Universe: Any
Prompt: Tony and Steve just hooked up and Cap is under the impression that things will be awkward from then on out, but from the first day on, Tony proves him shockingly wrong by being the hot Italian lover every woman dreams of.
Bonus Point: Tango. Steve being the female part. (I’d die to see that!) also, very dominant Tony while doing so.

Universe: Any
Prompt: Loki cast a spell or Steve so he falls into a coma, saying that a kiss from a true lover will wake him. All in while Tony goes ballistic and tries to find all possible way to wake him, but falls in love with him in the end and wakes him.
Bonus Point: Steve had a crush on Tony before the spell.

Universe: Avengers or Ultimates
Prompt: Steve turns back to being his sickly frail self and turning the people around him away, all but Tony. Even with this transformation (maybe Loki was the cause? Up to writer!) they begin to have a romance and Steve acts out the submissive part due to his size, but when the spell wears off, he still feels like it. 
Bonus Point: NSFW content when he turns back to normal Cap.