I thought Biggs and Wedge from Final Fantasy VIII were hilarious. Always bickering and always being demoted. They started out pretty high ranks and by the end, they were privates (I believe, though their exact ranks elude me) and ended up quitting.

On a side note, Biggs and Wedge from Final Fantasy VI were added in the PlayStation version of the game. In the SNES version of the game, they had Vicks and Edge instead.