Assign 'X' Sample, soundfont, synth, etc. into a FX Channel. Go to that channel and select 'Fruity Blood Overdrive' or 'Fruity Fast Dist'. Two simple FX's that come with fruity loops and can be pretty effective if used right.
If used right is correct. For the most part, I would use them in conjunction, with massive compressor/filter action. You might want to check out the Devil Inside - its a great VSTi that is produced by the same people who made Sun Ra, Baxxpander, Cosmogirl, and Elettronix. Check it out over at www.kvr-vst.com While you're there, get Bassline 2.0 - its worth the small download.