Unreal Tournament III

The "Top Gun" award is earned for killing an occupied air vehicle with another air vehicle.

Suggested Setup
Gametype: Vehicle CTF
Map: Suspense
Mutators: Speed Freak, Weapon Replacement (If playing against bots, all to Impact Hammer)

I would recommend doing this in split screen with a second controller, as it makes it much easier and takes less time. As soon as the match starts have the second player run and grab the Raptor on their side of the field and float it in the air in line with the bridge. Now with your player go and grab your Raptor, and simply shoot them out of the air with the :L1: missile attack. You won't get a notification on screen about the award, but you still got it. Pause and return to main menu, then repeat until you have the trophy.

If you want to do this against bots, put on Weapon Replacement with everything to Impact Hammer so that none of them are shooting at you with regular weapons. Jump on your hoverboard and book it over to the Raptor as soon as the match starts. Take it over and sit on top of the large building on the same side of the road as their flag and wait for a bot to hop in their Raptor (if one doesn't at the start of the match). Shoot it down for the award, then return to main menu and repeat. Watch out for a bot going to grab the Longbow then shooting it at you from on the bridge, as this can be a minor annoyance.