I use a Garmin GPSMap 188c with the fishing Hot Spots maps.

It's an older unit, no longer made, but it works very well. The Hot Spots maps show the approximate location of buoys, as well as contours, hazards, and fishing information from local reports.

The 188c is probably the lowest I'd go on the Garmin GPS units - anything less, like a 168, has too slow of a processor and doesn't show real time location. I know because I had the 168 and tossed it for the 188c.

Having a GPS at night, or even on a lake you've never been to in the day, certainly makes the experience more enjoyable because it helps you keep your bearings and away from hazards or shallow water that you don't know about otherwise.

I picked up my unit on here in the Boat Discussion forum for very cheap - spent a few extra dollars on a chip and some maps and was good to go! Total investment was around $300, which has more than paid for itself with the use I've gotten out of it!