It seems like https://www.speedrun.com/user/frommaplestreet used an aimbot in his 4h 48min run of UT2004. You can clearly see it at around 2min 33sec into the run where rockets fly way off the boresight of the rocket launcher.

I see nothing against it in the "rules" button but it doesn't feel like a true speedrun where such a method is used imo.