When someone plays Halo 3 so much that the Halo logo burns into their face. Such an accomplishment is very impressive.
Not to be confused with the Halo 2 tan or the Halo CE tan.
Jason: hey dude, what'd u do over the weekend?
Tom: z0mg d000d, lyk l0l, I g0tz a halo 3 tan!! u c4n practically see the hal0 log0 in my face!!!! lol
Bob: I got a tan this week.
Sam: How Man!, there ain't no sun here in Washington.
Bob: The UV light from my TV screen gave me a Halo tan!
Sam: Holy Sh*t! I see the halo logo on your f*cking face!