Bilbo. I would make him cupcakes and tea and sit cross-legged on the floor like a little kid while he told me stories of his adventures.
2. trust with the keys to my car:
None of these people would know what to do with a damn car, haha.
3. put thumbtacks on the chair thereof:
Elrond. Not because I dislike him or anything, I just think his reaction would be funny.
Faramir. He has so much goodness in his heart. I can't even handle it.
5. pack up and leave if they moved next door:
Clearly Sauron. His mere presence in an area draws dark and evil things to it.
Sam. He becomes the mayor of Hobbiton in the books so he has some political experience.
7. pick as my partner in a buddy movie:
The best buddy people already have their own buddies. Merry and Pippin. Legolas and Gimli. I'm going to go with Eomer here. He is so badass but is sort of on his own all the time. We'd go chop off orc heads then come back home and see who can drink the most ale before passing out.
This may seem random, but Aragorn and Faramir. In the book, when Pippin first sees Faramir he is reminded of Aragorn. They both want to do the right thing, but at times feel like they don't quite measure up. I don't know, this is a hard fandom to do this with because the canon pairs are just so perfect.
9. vote off the island and into the volcano:
Denethor, since he likes fire so much. Theoden lost his son too, ya know. Did he despair? Nope. While you were off killing yourself he was leading the charge to help defend your city!
10. wheedle into fixing my MP3 player
This is the same as the car question, haha. I guess Gandalf would have the best shot with any type of technology. I wouldn't get my hopes up though.