Bruce: You two do nerdy sciencey stuff. It sounds really typical and cliche, but you just love that he is so passionate about his work, and so he shares it with you. With that said, you guys definitely work on your, ahem, personal chemistry as well.
Bucky: You guys dance together. Sometimes you'll go out to a dance (I dunno if people still do that, but this is modern bucky) or sometimes you'll just crank up your stereo and dance to your favorite jams. There's also lots of slow dancing, cuz Bucky's a slow dancin kinda guy.
Clint: He takes you for hikes in the mountains. He likes being out in nature, so hiking is a good couples activity to do that. He also likes rock climing, so sometimes you'll do that.
Loki: Loki tries to teach you magic, or you'll both just talk. One time he decided to tell you about the criminals he was reading about, and he spoke with such admiration that you were scared of him being around knives for a while.
Sam: He will take you flying. Tony managed to make an addition on his suit that would let it carry two people instead of just one, and still be able to function normally, so Sam likes to show you the birdseye veiw of the city.
Steve: You'll go for little road trips on his motorcycle, maybe to a park or a small town, where you'll eat the picknick lunch you packed and just have a relaxing day. He likes to show you how eveything has changed since he was little, and he shows you places that he used to go to frequently.
Thor: You show him the local flora and fauna. He never gets tired of seeing new flowers and plants and things like that, and he marvels at how different they are compared to what he's used to in Asgard. And, because your a nature kinda person, you know a lot about plants and flowers.
Tony: You usually do some work together. like working on cars and such. One time you were fixing up an old car, but the part you were putting in was creating too much friciton to be safe, so you decided it needed some oil. But because you were totally under the car, you asked Tony to pass the lube, and him being the perverted guy he is, burst out laughing, saying how he had been waiting for you to ask.
Hey guys, sorry it's short and kinda crappy, I'm writing this while I'm home sick, so yeah. I'll hopefully write more soon. Bye!!