Bracket Style:
Play 5 games and get placed in a bracket (bronze, silver, gold, platinum, diamond) based on performance in the 5 games played. You can move up and down in the bracket, and you can be demoted or promoted to other brackets based on K/D and Win/Loss ratios. This has been implemented in Starcraft 2 and Call of Duty: Black Ops 2 with great success in both.
Halo 2-style ranking system:
Rank based on a number from 1-50 that is determined purely based on Win/Loss ratio in games and not determined by K/D. You can lose and gain your rank. In Halo 2, this was a very clear indicator of how good someone actually was at the game. I recall being able to at least pinpoint someone's ability at that game based on their level.
****I personally would prefer the Bracket-style ranking system because I believe it to be the better indicator of skill since it takes into account K/D and W/L.
-
BUNGIE'S BIGGEST MISTAKE WAS NOT HAVING A COMPETITIVE RANKING SYSTEM IN THIS GAME THERE IS NO FEELING OF COMPETITION ANYMORE, THERE IS NO GUARDIAN VS GUARDIAN - ONLY WEAPON VS WEAPON, SUPER VS SUPER AND GEAR VS GEAR.