Ikr

Shortened version of "I know, right?"

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

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?"