uh, weapon bob makes no sense and absolutely kills my hitscan.  disable that.  blandingshake - get rid of that, its *some* of the annoying shaking.
mouse acceleration - even disabling mouse smoothing and mouse accel in ui does not get rid of it in game for some reason - have to do it in ini - getting rid of that increased my hitscan 50%
Magic red eye removal - the red circle of damage and blurring - i already know im getting hit, thanks
sounds - gah  - i had the most deaths by roadkill for a while until i up-ped my vehicle sound.  also started walking around with an avril all the time.  The weird thing is some people dont need to make these changes to hear the sounds correctly and others do - it depends on your sound card and driver quality.  My on board audio is actually better than my x-fi at default settings.  

Mouse tweaking - after disabling mouse accel in OS/Registry and in game and in mouse driver (why my logitech gaming mouse has mouse accel enabled by default i'll never know - almost returned it until i found that setting in a menu 3 levels deep) , it takes a week or so to adapt but its well worth it for accuracy

most ut3 ini info here:
http://www.tweakguides.com/UT3_7.html

disabling mouse accel here:
http://forums.epicgames.com/showthread.php?t=605871

Win7 mouse accel disabling - note, make sure your mouse is set to 6 of 11 on the cpl lider bar.
http://www.esreality.com/?a=post&amp;id=1846538

General mouse tweaking - from a CS guy, but hitscan is hitscan
http://www.overclock.net/mice/173255-cs-s-mouse-optimization-guide.html

lol actually spent a full day on this once getting everything right.... well worth it