Get a Boomslang!!
You can adjust sensitivity on the fly (the Boomslang sensitivity setting, not the UT game sensitivity setting).
I was in a big instagib CTF game with the Stallion last night (I know how you feel about instagib CTF Rooster, but I don't get to play with Stallion that often, and a bunch of my other PuF friends were there. Besides, it turned out to be tons of fun).
Anyway, I have the sensitivity turned up real high so I can spin around and do some twitch shots (or try to do twitch shots). By "real high" I mean Boomslang sensitivity at 8.5 verticle and 10 horizontal (yes, seperate settings), and UT sensitivity at 2, and I don't remember what the window setting is set at.
Then I go out in front of the base for some aggressive defense. I hold down the thumb button and spin the mousewheel a few clicks down and my Boomslang sensitivity is immediately lowered. Now I can get superprecise aiming on the bad guys from far far away. All of a sudden a few of them rush me. I hold down the thumb button and spin the mouse wheel up up up up, and max out my sensitivity (I have the UT mouse sensitivity at 2, so it doesn't get ridiculous when I boost up the boomslang sensitivity). So now I am supersensitive and I can spin and dance around and try to twitch shot people.
Imagine if one of you guys with skills could do this. This has some serious potential.