If you're worried about the level cap:
http://www.fallout3nexus.com/downloads/file.php?id=121This mod increase it to either 30 or 40, you'll need this to make it work fine:
http://www.fallout3nexus.com/downloads/file.php?id=165Else there's a chance you'd end up locked in the level up screen.
Alternatively, there's this:
http://www.fallout3nexus.com/downloads/file.php?id=96Which is probably better since it just increases the experience needed to level up, so not quite game-breaking, I don't know if it'd take too long to level at high level though.
I actually haven't tried them, so I'm not sure how they work, they seem to though.
Here's something for those who think VATS is overpowered:
http://www.fallout3nexus.com/downloads/file.php?id=68You'll take as much damage in VATS as in realtime, so now there's actually a disadvantage to it since you'll be vunerable while doing it.
No mod that removes the slo-mo yet.
Also, FO2's cap was 99, but you'd be crazy to actually grind that much, FO1 was 21.