Scott- Anything lacy. He likes how delicate and fragile it makes you look.
Stiles- His boxers. It gives him a sense of pride when he sees you in them, especially when you're walking around after you've done the do.
Derek- Anything you're comfortable in. He likes to see you happy in your skin, and isn't that bothered because he'll just be taking them off anyway.
Jackson- None. He loves it when you hint that you've gone commando. Leaves him curious to see it you've stuck to your word. Which you have. Regularly.
Isaac- Thongs. Being shy and quiet, the idea of something so skimpy is sinful to him. And sinful is sexy when it comes to you.