"Not Fit for Human Eyes" - Have the Texture Browser crash 20 times, for no discernible reason.
"Still Not Fit for Human Eyes" - Have the Model Browser crash 20 times, for no discernible reason.
"Patience is a Virtue" - Force-quit Hammer 10 times while it appears non-responsive, but is nonetheless still compiling your map in the background.
"To the Max!" - Reach or go beyond the maximum entity limit in a map.
"To the Max - EXTREME!!" - Reach or go beyond the maximum brush limit in a map.
"Crash Course" - Crash Hammer 1,000 times. The means of doing so don't matter.
"Invalidity" - Create 1,000 invalid solids.
"Carve my Heart Out with a Knife" - Carve 500 times in the same map, then attempt to compile.
"I See Rainbows!" - Create a leak into the Void larger than 128 HU^2, in a spot where players can clearly see it.
"MY EYES!!!" - Compile a fullbright map.
Just for fun:
"That's Gotta Hurt!" - Compile a map that is entirely covered by a single trigger_hurt brush.