"By Kord's bloody blade!" is one I like to bellow out every once in a while. It's particularly impressive coming from, say, a halfling bard. ;P
"Hieroneous, guide me!" is one the NPC fighter/cleric in one game I'm in uses a lot.
"Whaaaat?" is the favored phrase of a rogue in another game.
"Go for the eyes, Boo!" keeps popping up, as does, "Our cause is doomed," and "I care not!"
-The Gneech