The rpg can effectively deal with both the FP and Scrake, and aoe damage helps for groups of trash
The demo is also a big zed killer, greatest at it probably.
The gunslinger is a pretty great perk, it's a competent big zed killer, it deals pretty high damage, runs fast and just a good all-around perk Weapons are all single shot (except for the FAL) and ammo is pretty costly compared to most perks. So I understand the sharpshooter is primarily a big zed killer being able to dish out the highest damage on a single target (last i check in the wiki the m99 deals more damage than rpg) and of course has incredible headshot damage, but maybe it's just me but this perk seems to have really limited trash killing capability. No offense to anyone who has this as their favorite perk.