I adore In All The World (http://archiveofourown.org/works/401038) by wallhaditcoming. There is also a podfic (linked form that page) of the story by kalakirya which is wonderful. (In case you aren't familiar with the Sentinal fandom, neither was I and I didn't need to be to enjoy the fic - what you need to know is all explained in the fic itself)

There is also Citrus and Woolen Blankets (http://archiveofourown.org/works/836917) by Princess_Aleera, which is initially Tony/Clint, then evolves to Tony/Clint/Steve.