Badass Bookworm: Well-versed in history and an airline pilot, also very physically fit and talented.
Ballad of X: "Ballad Of Mutt", from the Tattooed Millionaire single.
Berserk Button: He's very protective of his voice - understandable, since its how he earns his living. So when he catches a wiff of someone in the concert smoking, he'll drop everything to yell at them.
Captain Morgan Pose - The Iron Maiden Greatest Hits DVD collection includes some behind the scenes footage where a sound tech points out the features of various band member's monitor speakers. Bruce's are a) not actually used (he gets his monitor feed through an earpiece) and b) bolted down to the stage, so he can do this. Or jump on them. Or use them as a banked surface to run on.
Cluster F-Bomb: Swearing is generally not something he goes all out on, but should you hurl things at him (or the band for that matter), abuse the fans or commit unspeakable atrocities, don't be surprised when he belts out one your way. See Berserk Button on this page too.
Evil Laugh: He does this in a lot of songs. "Bring Your Daughter... to the Slaughter", "The Evil That Men Do", "Can I Play With Madness" and specially "Fear Of The Dark" come immediately to mind. Of particular note, "Moonchild" climaxes with a bone-chilling, prolonged evil cackle from him.
Honor Before Reason: When Bruce found out his then-wife had slept with a member of Mötley Crüe, he challenged Mötley Crüe guitarist Mick Mars to a fencing duel. Mars was confused, as he had not, in fact, been the one who slept with Bruce Dickinson's wife. That was bassist Nikki Sixx.