CIMM
An acronym that stands for "Chuckling In My Mind" which is generally used in an attempt to deviate from usage of overused internet phrases such as "LOL" (laughing out loud), "LMAO" (laughing my ass off) or "ROFL" (rolling on floor laughing). It can even be considered more genuine amongst your peers, because in reality it is highly probable that you are in fact not laughing out loud from your computer chair.
Buddy: "Dude, I totally tripped and fell on a toy car in my living room earlier."

Buddy 2: "Are you okay?"

Buddy: "Yeah, I'm fine. You know that I'm like a modern day Superman!"

Buddy 2: "CIMM."

Buddy:"Yeah dude... So anyway, I'm going to go watch porn. Kthxbai!"

Buddy 2: "LOL!"