Garmin. Any Garmin you can find for under $200. And don't make it your main tool for navigation either. Bring along a good set of topo maps of the area and a good reliable compass. Know how to use both before heading out. I never rely soley on my GPS, ever!
I have the garmin legend hcx with topo maps loaded into it it came with a case a sd card and topo maps it's simple to run and batteries last a long time in it as stated above get a topo map of the area you are hunting it allows you to see a larger area at one time than the gps the screen is about an inch and half square
I've been using the basic model Garmin Rino, which last I checked was still under $200. It's got a built in radio and you can transmit your position to other Rino users, which it then displays on the map. But the basic Garmin line is about all I've used in my professional and personal adventures since the mid 90s.
As a Taxidermist I look at hundreds of Whitetail Bucks every year. I know that I have seen many different ways people judge the size of racks on live deer. I think for the most part they all are pretty close. I'm going to give you some measurements that I have noticed being right on in just about every deer. We have used it in the last couple years and have only been off by about 5-6 inches. We do study the deer while bowhunting so we get a little more time to look at them....