Boards
Things have you have borrowed and never given back.
1) A copy of V for Vendetta (the book), borrowed off my then long-distance girlfriend. We broke up via email, I've never seen her again, so I guess it's mine now.
2) A volume of three novels by BS Johnson, borrowed from the boyfriend of a former colleague. First they moved away, and yesterday I heard they've split up, so I doubt very much our paths will ever cross in future.