Which is the most common internet abbreviation you often use in email/chat?

I tend to use things such as: LOL, brb, LMAO and a few others. However I try to avoid abbreviations at all costs because I know there are many English learns I know and it is not good to write like that because I know they will be expected to write properly. Plus I know how to type fast and I don't always like to write abbreviations because I can type just as fast without them. I think people use abbreviations a lot because they cannot type fast on the computer or if they are using SMS it is faster to use abbreviation because most phones don't have a keyboard like on the computer. Have a nice day.