I think the slow motion effect should be similar to that of Killing Floor where when a zombie or whatever is attacking and the player pulls off a good shot on them it slows the entire game down for a second or two.. Either ingame or just in the replay I don't know. Ingame it would have to be only for major hits and/or dismemberment because otherwise the game would be all slow motion. In a replay, it would be nice to have the slow motion effect apply to the same principle of major impacts. Maybe something like Bez Cam can be incorporated with that.