I don't care too much about whether this involves disabling gore or not, but I'd like to have time-flow constant, especially as long as enemies are still around.
In game settings, you can change the kill camera setting to Always, Last Enemy Only, or Off.
This only applies to kills outside the VATS system though. VATS use will always result in slow motion kills and can only be removed via third-party mods.
If you are on the PC, I believe this mod located on the Fallout 3 nexus will go partway to solving your problem. While it doesn't eliminate the slow-motion effect, by preventing the camera changes, it substantially reduces the duration of the VATS sequence. You can see it in action in this video. Keep in mind however that, in Fallout 3, you receive 95% damage reduction while VATS cinematics are active, so there's an advantage to the slow-motion view in this case.