Well, that depends on what you plan on doing with the rack.
If you want to look cool and actually carry something then Yakima and Thule seem to be the most popular. A lot of the guys here run those and will add a cargo basket and whatever else to them to make them fit their needs.
If you want to look cool and not have as much versatility and cargo capacity the hit the wrecking yards to see what you can find off another vehicle. XTerra racks are cool and have been done here. I tend to favor the old school chrome and stainless racks for a bit of a retro vibe.