iChat
Used by 38 peopleen.wikipedia.org ↗

“For chatting I use iChat on my MacBook.”
Chloe Cross Interview, Writer (VICE) · via Uses This 
“We make regular use of AIM (for me, via iChat) in the Pitchfork office.”
Mark Richardson Interview, Editor-in-chief (Pitchfork) · via Uses This 
“I also use iChat for IM.”
Mark Jardine Interview, Designer (Tapbots) · via Uses This 