Linkinus
Used by 5 peopleen.wikipedia.org ↗

“I also sit on a private IRC channel throughout each working day with some of my closest friends from my university days, and I use Linkinus as my IRC client.”
Matt Gemmell Interview, Mac and iOS developer · via Uses This 
“Linkinus is my preferred IRC client.”
Ed Finkler Interview, Web developer (Gimme Bar, Spaz) · via Uses This