From Cyanide and Happiness, this rendition of 'I don't give a fuck' is made more epic shit. Used when you want to really show someone you don't even give a flying fuck what they think.
A: I got a new phone B: Shut up
A: It's twice as-
B: I don't shit a fuck!
A: But the processor
B: NOOOOOOOOOOOOOOOOOOOOOOO
I don't give a shit is a popular phrase to be used when you are not interested in what someone else says or believes. It implies that you don't even care enough to physically give them a sample of your fecal matter.
Gamer 1#: Dude your computer sucks, you shell out $2000 for a kicass rig, and still run it on a piece of shit CRT monitor.
Gamer 2#:Well that may be but honestly, I don't give a shit.