I like to wear the Rivet City Security Uniform plus the Police Cap (unique apparel item found in the DLC Broken Steel's Presidential Metro), plus lucky shades, plus Chinese Assault Rifle.
OR
Regulator duster, pre-war hat, lucky shades and backwater rifle. I pull of headshots like there's no tommorrow. (Keep in mind I use this in FWE with the damage multiplier pretty high, so you can't really headshot someone once in vanilla and get a one-hit KO)

I like to RP wasteland justice.

Just recently, I started a new game with restrictions (see my "Making Fallout 3 More Challenging" Thread for more details.) Lucas Simms was killed by burke, but after, I killed burke, and now, I am the new sherif of megaton! I look so snazzy and western with my Leather Armor, Sheriff's hat, and hunting rifle.

General chases armor from mothership zeta

I just swiped Zip's unique outfit by slipping him some Talon armor (I always have a few suits from the assassins I kill), and I'm going after his headgear as well. And since I have the Animal Friend perk, mole rats won't attack me so I can hang out with them. ALL HAIL THE MOLE RAT KING!!