Purigen, chemipure elite, lava rock, biomax, matrix, pot scrubbers.
In my xp3 I have the 30 and 20 pads that come with it, biomax, purigen, chemipure elite, a microfiltration pad, a super microfiltration pad, a 50 micron filter pad, and an 18 watt uv sterilizer on a 55 gallon tank. The water is amazingly clear, but I doubt I really need all that to make it that way. I'm guessing it's probably my healthiest tank with all that help.
All my other filters/tanks I run the standard filter pads, some combination of biomedia, purigen, and a fine filter pad.