I actually thought it was quite a powerful ending. I went down fighting, and fight well I did. But something changed as I thought. I wanted to kill those covenant and make them pay for what they did, but after 10 minutes of increasing amounts of enemies, depleting ammo and being backed into a corner, I'd lost all will to keep playing. I knew I was officially fucked, I just wanted to escape.
To bring about that sense of feeling in a game, its not easy. But I couldn't escape, so I hoisted the gun, sprinted at the nearest group of elites, and went down bashing the living shit out of them.
No spartan could ask for a more fitting death.