Fungot is more or less the mascot of Freenode's #esoteric channel. While not the only bot on the channel by far, it is the most advanced and only regularly present one which has been written in an esolang.
Fungot also responds to mentions of its name (lowercase) with Markov chain-generated answers in several selectable styles.
Fungot commands are invoked with the caret (
^helplists all built-in commands;
^showlists all commands, including user-defined ones.
^bfruns a brainfuck program,
^ulruns an Underload program.
^deflets you define a user-defined command in brainfuck or Underload,
strlets you define commands whose source is longer than an IRC line.
^stylechooses a Markov model for random Markov chain responses, or lists the available models. Creating such models is now a lost art.