From the description:

Up close and personal, that's how you like it. Your sneak attack criticals with pistols, revolvers, and submachine guns, whether guns or energy weapons, all inflict an additional 20 percent damage.

Does this includes SNIPER RIFLES?

No. I don't have the perk, but it doesn't mention rifles.

pistols, revolvers, and submachine guns
pistols, revolvers, and submachine guns
pistols, revolvers, and submachine guns
pistols, revolvers, and submachine guns
pistols, revolvers, and submachine guns
pistols, revolvers, and submachine guns
pistols, revolvers, and submachine guns
pistols, revolvers, and submachine gunspistols, revolvers, and submachine gunspistols, revolvers, and submachine gunspistols, revolvers, and submachine gunspistols, revolvers, and submachine gunspistols, revolvers, and submachine guns

This.

So no Rifles :3

so yes????????? thx!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Oi, don't give the OP a hard time, even in jest - I live in the UK and have absolutely no idea what category half the weapons in fallout are despite playing the series since the beginning, and just don't ask me about different types of ammo. The only gun I've ever seen IRL is an air rifle (which I think is what you would call a BB gun, but I'm not even sure about that). It's a steep learning curve.

Didn't Leon train Matilda into using a Sniper Rifle?

Just sayin...

Now that you mention it, it would make alot of sense... but alas, no sniper rifles fall under the perk's category.