Most of the High-End samplers (i.e
Native Instruments Kontakt), have many FX and Filters built in to really mess things up. You can always run your sampler, into VST effects units for post processing. One very important element you need (or is at least recommended) for sample manipulation is an audio editor. Fortunately, you already have CEP, which should provide you with more than ample editing capabilities.
If you are looking for more specifics as to what type of FX you need, the only limit is your imiganation. Here are some common ones:
Filters-We all love 'em. Very flexible, especially good swept.
Distortion-Skys the limit here. Everything from soft and fuzzy, to full blown overdrive, to the digital clipping variety (insert Bit Reduction plugin here).
Flange/Phase/Chorus-Need I say any more
Delays/Reverbs-(see: Flange/Phase/Chorus)
Vocoders-A staple in the world of sampling
And we could go on forever. The point is, try every combination you can. That is how great samples are made, Trial and Error. Remember there are no rules in sampling, the nastiest, trashiest sample could very well be the centerpiece of your next hit-single.
Another pearl-of-wisdom (not really). Sample everything you can. When jamming out, or just hanging about, throw a cassette into a cassette recorder an hit redord. You never now when something amazing will happen (like your drummer rips the absolute nastiest sounding bean-fart ever), and you will have captured it for your next album (I prefer cassette for sampling still as it imparts a certain nastiness and color to a sample that is really hard to replicate authentically on digital systems...a little nod to the old-school I guess).