Here's a few that I use.
First one's what I use for my spoilboard. 2-1/4" diameter. It's just like a slot cutter, without the bearing. I got it used for free, and cut the shank down with a grinder, as it was 4" long. It needs a little cleaning.
Vortex sells something similar, but they're not cheap.
Second one is a 1/4" "O" flute that I use for plastics. Works great for plexiglass, no melting. Sorry about the blurry picture. Got it from CNC Toybox.
Third one is just what you need to cut through 1" board in one pass at 1200ipm and 15,000rpm. 3 flute coated compression from Onsrud. Just got 7 of them in the mail today.
When cutting laminated particle board, the laminate is so abrasive that a good size groove will wear into the tool in as little as 20-30 sheets. I've cut 80 sheets with one coated tool without ay wear grooves.
Fourth one is a 2 flute upcut chipbreaker from Onsrud. Great for hardwoods and hard plywoods, as they cut with much less power required than a standard spiral bit. These are also really good for cutting deep mortises.
Last pic is about $1200 worth of router bits.