Watching my partner make bread is definitely one of mine and, in particular, watching his hands as he kneads the dough. It's beautiful and fascinating and such a turn on. Actually, watching him cook in general turns me on, haha!
There's another that I can think of off the top of my head that's probably a little weird? And I'm also not entirely sure when it started to get me all hot and bothered. But I noticed it almost immediately when he started teaching me how to play Magic: The Gathering; he would almost constantly shuffle his hand. I never found it annoying or anything (in fact, I've picked it up myself >.>), but now, if I play a game with him or I watch him play a game, him spike shuffling (I think that's what it's called? Not entirely sure; I can't remember the term that he and our friends use) his hand turns me on.
In fact, playing a game of mtg with him or watching him play a game of it, or hearing him discussing or suggesting cards that he knows, or seeing how efficient he is at deck building and how quickly he can make decisions as to whether a specific card is a good idea or not gets me all bothered and hot.
Something else I love to do is snuggle under his duvet when I'm at his flat; not only is being surrounded by his scent really comforting, but it arouses me as well.
In all honesty? Almost everything he does has an effect on me!
As Alastor said, the hollow in the collar bone... ooooh that gets me every time.
Is yours inside the V though? mine is outside!
Alastor, the "hollow" you have a penchant for — assuming it's the one either side of the neck — is the 'supraclavicular fossa' and the depression at the base of the neck is the 'jugular fossa' (incase you've ever wondered).
Wifey tells me it's my mouth, knowing what it can do to her and don't think she means tell her off.
Oh, God, yes. The OH and I used to work together and I'd watch him talk to other people and all I could think about was what else that mouth does. Very distracting.