it shows oyu a name when you create a multiplayer game. after youve selected characters, the map, the gametype, and your picking teams, or waiting for the game to start, above where your character names are, it shows your x-box, with a name above it. it can be many things, like
The Big L
Saucy
Bear
Noodle
and if your REEEAAAALLLY lucky, like me
your x-box will be named Donut, or Caboose. once it's chosen your name, it can NEVER be undone.(unless you delete all halo files...maybe...i havent tried)
NAMING IT WITH DOA3 IS FOR CHUMPS
Even though I don't have an Xbox, I gave all my game systems woman's name. Why? Because all of them are very indecisive. XD
GBA: Gretchen
SNES: Sarah
PS2: Jessica (after my old girlfreind, cause she is indecisive if she likes men or women XD)
NES: Naraku (not a woman's name, but it's the evil dude in InuYasha, and the NES hates me so it's evil)