Typhlosion, Jynx, and Rotom (I guess Mesprit and some other things can be used, too). Typhlosion hits like a truck when near full with Eruption, being able to 2hko almost everything when hitting neutrally (although pokemon like Hariyama, Mantine, and other normal Typh checks can easily deal with it). It has a nice 100 base speed for a scarfer, so it should get the revenge killing job done, too. Jynx can sleep opponents and trick them, too, unlike Typhlosion, but they're both SR weak and Jynx has horrible physical bulk. Jynx hits decently hard, but unboosted scarfed attacks aren't going to be breaking through a ton of things although it still can fulfill the role of revenge killing well enough. Rotom has a nice typing that enables it to take fighting, ground, and normal hits and it gets volt switch, as a means of fast momentum generation, but it's not too powerful and not as fast as the other two (albeit not much slower), too. In addition, it isn't hitting nearly as hard, but it still has its uses. Overall, it really depends on team as for which you pick. Also, keep in mind that if you have enough priority (Kanga, Liepard, Gatr, etc.) or fast pokemon (Archeops, Tauros, Sneasel, Heliolisk, Virizion, etc.) and a decent defensive core or checks to the common threats, then a scarfer may not be necessary on your team.