I just joined here, here are the two that annoy me the most.
People who bash ACU. Sure it doesn't work everywhere, but no camo does. ACU works pretty well in areas with dead vegetation, sand snow and rocks. The pattern was built around the same principal as multicam: Appear darker in dark areas, and lighter in light areas. It works fine in the right environments.
Another: Guys who think ALL gear HAS to be matched PERFECTLY, and if you have ONE different colored pouch on your vest, ALL your gear is crap and you suck. I am going to use a CB Blackhawk STRIKE LBE, and I have an OD ALICE rig already, which I use over various camos. Does it mean my gear doesn't work if it doesn't match the pattern? No.