A top end Garmin.
I have a 5 year old version of such a Garmin unit and it is a great tool, however don't forget a GPS unit can fail to triangulate in heavy cover, and batteries can go dead, or the unit just "die" .... also carry a quality, accurate map and compass. I like to use a topo and a "Google Earth" view of where I hunt. The combination works great for getting around. Laminate them and you'll have a durable map that will last for years.