The NOVA Open was one of the largest tournaments I've attended with about 88 players total in 40k alone. There was nearly every Codex represented and here are a quick sampling of armies I really liked.
First off we have D. Brown's Orks. This is a Blood Axe horde that sports some of the coolest conversions and bright colors. His style is a cartoonish without looking goofy. One of the coolest features of this army were all the berets and army hats the Orks sported on their green craniums.
Below you can see the Ork armies HQ choices. Check out the objective markers like the Ork Servo Skull and the Orkus Mechanicus Big Mek. What a goof ball!
Nobs that keep the boys in line.