Within arms length? The best I can manage is to smash someone with my keyboard, or possibly break my mirror and use a bit of that.
Otherwise, I'd say my sword, but that's blunt and totally impractical in a confined space anyway.
So really, that only leaves the kitchen knives...
Yeah, I'm not well prepared for someone attacking me.
Then again, I know martial arts, so who needs a weapon anyway?
Especially if my attacker is unarmed. XD