The Gun Runners recently developed a new round, more dangerous then any other bullet in the Mojave. The R.I.P. Round, featuring devastating damage with armor-piercing capabilities as well. They're expensive, so only the rich can afford them. Fiends and Legionaries haven't been able to get their hands on them yet. They come in 5 calibers: .22LR, 9mm, 10mm, .45 Auto, and 12.7mm.

R.I.P. Rounds do double the damage and pierce 10 DT.

This isn't actually just an OP ammo mod. RIP rounds are real, though they're pretty new and experimental. I saw them and thought they'd be fun in New Vegas, so I decided to add them for the hell of it. Picture (not mine) is of a real RIP bullet.