I just wanted to follow up on Nozza's advice. I had never thought about trying to get into the passenger seat when an enemy was driving a warthog until I read his post. The tactic definitely works.
It is pretty common for players to try to run you over with a warthog on Wreckage. I have actually used this tactic multiple times and you would be amazed at how oblivious the drivers are to the fact you are sitting next to them.
Cheers for thinking outside the box!