The secret's out. We already know you guys have named your iPods and your cars. So there's no reason your GPS should have to go name-less.
Name it after its country of origin. GPS units come loaded with a few different accents, but you can download tons more for a truly multi-cultural baby. Use its accent as a guide to choose a local name. British Names: Abbey, Kinsey or Phillipa for a girl. Nigel, Langdon or Tanner for a boy. Irish Names: Brigid, Fiona or Sinead for a girl. Cillian, Patrick or Riley for a boy. Australian Names: Kyleigh, Terri or Melba for a girl. Aiden, Baz or Shane for a boy.
Give it a "family" name. Everyone likes to have a name that's connected to their family heritage. Give your adopted GPS unit a name that taps into its branded roots. For a Garmin: Minnie or Garry. For a TomTom: Tom. For a Motorola: Moe, Tori or Otto. For a Magellan: Magellan or Maggie.
Go with initials. Spell something out with your GPS' name. If it's a freaking retarded electronic device: Fred. If it's just your trusty GPS: Gina Patricia Smith, Gordon Patrick Sanders or just Geeps.
Name her after someone you don't like. That damn GPS is always yelling at you and telling you what to do. So name it after... Your ex-wife. Your annoying neighbor. An unfavorable politician.
Use a pop culture reference. Having your tech gear talk to you feels like you're in a movie, so why not give your GPS a name from pop culture. If she "knows it all": Clarissa If he's becoming sentient: HAL 9000 If he helps you fight crime: KITT
(Top GPS Image: Flickr member Jobriga licensed for use under Creative Commons)