@tinuviel I'm on a yes/no on this one. Yes, you can pretty easily find something for them to do. Sometimes, realistically? It's gonna be 'find a secondary skill to focus on', like driving the getaway car/etc.
The concept of a sniper typically relies on knowing a target is going to be at a certain location at a certain time and taking them out, or in defense of a specific position/ground to be held against attackers.
In my experience, very few scenes on a game are structured that way. Many consist of '...and in the course of a seemingly normal evening, OMFG SHIT JUST GOT REAL.' That doesn't leave a lot of room for snipers to be snipin'.
This is no different from being on a game in which people who translate ancient lore or research the shit out of creepy weirdness are a thing. Not every scene is going to give them a moment to use that specialization, and it shouldn't. Giles McBuffyTrope is not going to be Mr. Useful Skill At The Ready in a scene where the group wanders into the midst of a gangland shootup, or the coffee shop gets robbed -- and, frankly, neither is the sniper as a sniper (though they'll likely be more useful since they know how to generally operate a firearm in general as well).
So, yes, it's possible to give them something to do that plays to their strengths -- for instance, Giles McBuffyTrope might, with his understanding of symbolism and anthropology, recognize some element of whatever the gang's logo is from generic art or cultural history and know, 'Oh, these dudes are sporting a reference to Norse culture that's big with Neo-Nazis', even if the usefulness of that info's going to vary. Similarly, Ms. Sniper Be Snipin' would need to be pretty damned good at situational awareness, and may make the best lookout in the group, taking advantage of her well-trained perception... just not her snipin'.
Throwing in something for someone to snipe from the rooftops, though, is as unrealistic and unreasonable as deciding that suddenly the gang just has to be a group of supernaturally-affiliated cultists just because Giles showed up and needs something to do, or the character who specialized in being a seamstress needs a chance to give Grouchy McBikerchaps a tux fitting.