LOL

Stands for "League Of Legends" (game) or "Laughing out Loud".

"My favorite game is LOL!"
"That was funny! LOL!"

Air

Shortened version of "Am I right?"

"School is useless, air?"

Ikr

Shortened version of "I know, right?"

"The new Ubisoft game is awesome!"
"Ikr? It's very interesting!"