The Butterfly Halo 1,2 or 3

Using the BattleRifle and a button combo you can launch an opponent as high into the air as you want. As long as you continue pressing the buttons they will continue to rise, the glitchy part is that no damage will be done to the opponent.
Tutorial: The Butterfly - Grab a Battle Rifle and then fire once. Press the RB button (Right Bumper) and then quickly press the melee button. Keep doing this sequence fast while under an enemy and they should (If done correctly) "float" up in the air for as long as you continue to do the glitch