I'll always take freebies, however functional they may or may not be. Pens and pencils are great, bottle openers are always useful (got about seven free bottle openers from my student bar, all of them are also keyrings), posters are good, anything really.
The most useless freebie I ever got was a keyring advertising James Cameron's Avatar. A big silver block thing with cut out letters that light up in blue when you press a button... sometimes, when they feel like it. Mostly it just flickers and dies within a few milliseconds. So that's useless. Trebly so because it's way too big to use as a keyring and I don't care about the movie/game/whatever it is.