For the eighteenth day of my 25 Undead Christmas presents I want a Garmin Rino 530 .
As long as the GPS satelites keep chirping this two in one unit will provide both detailed GPS data on where you are and what direction your heading as well as the ability to listen and scan for others who may be transmitting. Another awesome feature is that you and other members of your party can transmit your location directly through the Rino so you always know where they are. Great for when you hear the gunfire and they don’t have time to scream for help. You’ll know exactly where they are.
On top of this you can plot out paths and waypoints, so if you find a “safe” path you can follow it again, no matter what the weather or lighting.
I know I am going to get some hate mail for this, but the satellites will keep running for some time after the apocalypse starts, and you might as well get as much usage out of them before they stop working as possible.