Natasha
Natasha always had a little crush on her partner. It wasn't because he looked good. Clint was the first person who looked at her like she was something other than a weapon that the Red Room made. So when Loki took him, Natasha vowed to get him back because she wouldn't let him turn into a weapon for a maniac. Clint always soothed her nightmares with his dorky jokes and sarcasm.
Tony
Tony developed a crush on Clint because they were very similar. Their personalities. It also was a bonus that the archer looked good. But what really drew him to Clint was that the archer easily looked pat his well constructed mask, something even Pepper had trouble doing sometimes. Well if he and Pepper ever broke up, he will give it a try.
Steve
Steve found Clint very fascinating. He knew the archer was good at what he did without any enhancements. He had a little crush on Clint. It was because in some ways Clint reminded him of Bucky. Clint like Bucky could get Steve out of his shell. He also took Steve to meet Peggy after Battle of New York.
Thor
Thor could understand why Loki chose to take the hawk. Their archer had a very big heart and he did not seem weary around Thor even after Loki. Thor is the only Avenger besides Lady Natasha who knew the archer had a brother and Clint had a bad relationship with him. Clint explains everything about Midgard to Thor. His patience is admirable.
Bruce
Clint is the first to realize that there is something more to the Hulk than smashing. That makes Bruce like him a little more than others. It also makes the Hulk protective over his Cupid.
The Avengers knew Their Hawk was one of the things that held them together.