I started a new game, killed Doc Mitchell, killed Victor, killed everyone at Sloan, ran through Quarry Junction, killed the guys at Silver Rush with a Plasma Pistol (proud of that one), killed the robots guarding the The Strip entrance, killed everyone at The Strip, killed everything in Lucky 38, then finally brutally killing Mr. House. Half an our was passed and i ended at level 4. Normal difficulty.
Man, did i feel like a man after that.
O_O I was level 22 by the time I'd cleared the strip on my "lol kill everything" run through! I had stopped at McCarran, Forlorn Hope, Nelson and Hoover Dam mind, but still, way higher than level 4...I think I got to level 8 or something before I even reached Novac (oh Mojave Outpost got attacked too...)
The best bit was by the end of it I was still neutral with pretty much everyone. Disguises + sneak + one shot kill = awesome sauce.