I've used Garmis GPS units in my planes for years. Started with a GPS 195, then a GPSMAP 196. When that was stolen I upgraded to the GPSMAP 296. Both the 196 and the 296 have an automotive and marine mode as well as an aviation mode. Getting one with the aviation databases in it would be overkill and expensive, unless you are or are planning to be a pilot, but all of the Garmin stuff is built to rigid standards and they are the most popular in the aviation world where dependability is a must.

Whatever you decide on, look for the ability to pick up a large number of satellites, 12 minimum. The more satellites it can receive the better it's going to be at getting and keeping the signal. Also be sure to use the external antenna, as the satellite signal is strictly line of site.

Have fun. They are great little gadgets.

Disclaimer: I do not work for, nor do I have a financial interest in Garmin, (although their stock is looking pretty good!)