Reaver drops were super annoying. Some friends I played regularly with at school liked to do it, forcing me to always keep a Siege Tank some distance from each resource cluster. One friend was particularly fond of Shuttle+Reaver micro (and their even more annoying cousins, Shuttle+Reaver over a cliff, and High Templars cliff drop), forcing me to commit two tanks per base.

As you can guess, I was a Terran main. While my recipe for Protoss friends was plain heavy metal, I took my frustration out on Zerg players. One thing I loved to do was to have two science vessels cast Defensive Matrix and Irradiate on each other, and fly them over enemy drones. People who haven't seen it before got mightily confused by what's going on. Doubly so when they decided to throw a "quick reaction" Mutalisk squad at them, only to watch them all die.

(That was even funnier than calling in a nuclear strike and flying a building over the red blinking dot to hide it. You'd think a random Engineering Bay floating in enemy's main would be a clear giveaway, but people always got so stressed by the "nuclear launch detected" warning that they couldn't connect the dots in time.)

SC:BW was a game like no others.