Go on any level with the skill berserk and kill an enemy with it when its does 
the slow mo bit where they spin round in the air. Quit the level and and go back 
on any other level (on any of your saves) this will make all the enemy go really 
slow and you go at normal speed and makes for easy kills! 

Note: fmv will go slow as well 

Submitted by mealonat at branstoncc.lincs.sch.uk