I knew when I went into the Navy that I wanted an avionics job - fuckin jets are cool.
I started out undesignated (thanks MEPS), and got put into V2 on a carrier (USS T Roosevelt CVN-71) working with ABE (Aviation Boatswain's Mate, Equipment) on aircraft launch and recovery equipment (catapaults).
I hated life.
Then I was standin watch with an AT that works in AIMD (Aircraft Intermediate Maintenance Division, they don't work on the planes, they work on the shit that goes in them), and decided to test into it, and did.
Everything else was gravy
Supply/personnel jobs suck - comm jobs can suck too, but at least you might get some applicable experience if you're a CIS major or something - do something exciting!