I use a variety sometimes, depending if I know how I'm going to play before I enter a match, or if I get a couple new ones that look neat.
Though the main one I like to use is "All Your Base" call sign. Has some naval ships in the backround (think a carrier and a type of cruiser). With that I'll use the skull and crossbones that has a bandana and an eyepatch as my emblem.
Pirate of the High Seas ..... ARGH!
Right now though, I'm using Techno Killer with the non-moving Stealth Bomber emblem. Looks pretty cool.