Let's see...
Brenn (duh)
Brendolus (girlfriend's friend gave me that one)
Warren (I look like a warren, apparently)
Paw Paw Brennan (talking about ye olde days on facebook once upon a time)
Brennagan (my dad, wtf?)
Breanna (lovely parents, eh?)
Among many I forgot

How the hell's Brennan a nicknameable name?