Goðafoss is a waterfall that seems to fly under the radar for absolutely no reason. It's a small, but very wide waterfall that's very photogenic.
The parking lot for Goðafoss is clearly signed and you'll be able to see the falls from the parking lot. Just take a quick jaunt up to the falls and find your perfect angle!
Since it was on the backend of winter when I visited, there was ice frozen into spirals on the rock which was really awesome to see. If you're lucky, you might see some reindeer while you're in the area as well!