Im looking for a gps only that shows contour lines of lakes.  I know they have the gps/ fishfinder but i was wondering what kind is the best for this.  Thanks!

Look for the "Plotter only" models from each mfg.

The contour lines are added map software that is available pre-loaded or as an internal memory addition-like Garmin.

Lowrance and Humminbird can be ordered with added mapping or can use mapping software contained on memory cards.

You have to determine of any available software has the bodies of water you are interested in and which mfg can read that software.