I would go with invisibility. Time travel can mess stuff up.
EDIT: I'm glad this is back. Many memories in this thread.
-
I guess time travel implies an ability to travel through both time and space (otherwise you would die after your first jump), so like someone else said, I would go to the future and access invisibility there, pick up some other future tech, go back to present time and sell it. I would be rich, the world would advance more, anf I could still have my wacky adventures.