YTFB!

In full it means "Yeah the Fucken Boys". A term used by "the boys" most commonly. The phrase is usually heard in Australia.

Friend: Did you hear Matt pulled a mad skid yesterday
You: bro......
Friend: YTFB!
You: YTFB!

R6 Siege

A shortening for "Rainbow Six Siege". Normally used when typing out the game title.

Friend: Dude, you wanna play some R6 Siege
You: Yeah, bro... let's not play ranked though