Best mid/top main?

Lissandra, cho, and that's all I can think of right now

Chogath is pretty flexible but if you are talking op and/or meta picks, jax could go to either lane depending on the match up.

Ive seen zed top and mid as well. Also yasuo but most top laners beat him easily.

Edit: forgot heimerdinger

Probably jayce is a good pick.

How about mid laners good in other roles?

Why not Kayle? She does well in pretty much every lane, and there are at least three different (and viable) builds paths you can use with her.