I hate to asshole up the thread so early on, but with countless hours invested in the game (like, no doubt, many here), I can't narrow "my courier" down to just one courier. I can probably whittle it down to two, though, so as not to look like quite so much of a self-involved jackwad. So.
The thinly-veiled player-self-insert courier:
Aaaaand the charming social-Darwinist schemer courier:
I just started replaying New Vegas with a new courier: Tseng, my perceptive, lucky prospector with a heart of gold and a love of Old World tech, especially anything laser-related. I imagine something like this theme song could be found blaring somewhere in the Big Empty, and it definitely fits his combat style (currently level 8 and rocking the MF Hyperbreeder Alpha and a fully modded Laser Rifle):