A lot of games utilized the 16-directional pad, most notably every sports game. Also, Utopia, Sea Battle, Armor Battle, B-17 Bomber, Space Spartans, Tron Deadly Discs, D&D, geez I could go on...
This is the sole reason I've held off in putting an Intellivision emulator in my cab with 8-ways. (and the plethora of buttons that would be needed for a lot of these games). A stained wood Intellivision bartop sounds like a good future project, with the right controllers.