Recently I've been playing gtetrinet, against the publicly accessible server at tetrinet.debian.net.
If you're unfamiliar with the game it is a multi-player variant of Tetris. You clear many lines and your opponents suffer. Want to make them suffer some more? Use the special blocks you acquire.
Special blocks? How about shuffling your opponents playing field? Adding new semi-formed rows? etc. All good stuff.
There is support for up to six players. To fire a special block at the player in field 1 you press "1". To fire the special block to the player in field 6 press "6". But to fire a block at yourself, to clear your playing field ("nuke") or remove a single line ("clear") you have to know what player-number you are, which will change from day to day, as it is literally a marker for the order you joined the channel in.
It seems obvious that there should be a special-case keybinding "fire to self", and indeed there was bug #291844 filed in 2005 saying as much. I've just submitted a functional patch to resolve this, and already my playing is getting better.
Join me sometime.