qq

In the Russian part of the internet, "qq" is an acronym for "coo-coo", which sometimes stands for "hi" in Russian.
Sometimes can also be just a single "q".

*person1 has joined the game*
<person2> qq
<person1> hey

LV

In the Minecraft mod GregTech, LV stands for Low Voltage.

Shit, I just burned all my LV machines!