The informal right to brag and boast about an achievement you've made. You get this right after you've achieved it.
If you make it up, you might get away for a while, but you'll get bashed if they find out you never earnt this right.
Geek A: *Three headshots in Counter-strike in 30 seconds*
Geek B: Bastard, you shot your own team mates
Geek A: But it was still 3 headshots, that means I get bragging rights
Geek B: You're a load of shit, no bragging rights for stupid noobs.