[Xplo]

In a cinematic game, sentry removal could be done with arrows; a headshot might kill or knock out instantly, while a neck or vitals shot could simultaneously silence and incapacitate a foe, or a two man team could have one member snipe with arrows and another move in for the kill while the enemy is surprised and in shock. The arrow could also be poisoned; why the hell not?

Likewise, poisoned darts from a blowgun, airgun, spring gun or the like could work in a cinematic game. All these methods would be silent or nearly silent; no silencer needed.

Realistically I don't think any spec ops guys seriously train in archery, except maybe as a hobby, and it would be easy to miss someone's head with an arrow in the dark at 50 yards. Arrows wouldn't necessarily prevent someone from screaming, using the radio, or punching an alarm button - even with a head, neck, or lung shot - and any dart that can fly more than a few feet would probably be noticed, and no poison would work fast enough to kill or incapacitate the guard before he could react.

Sneaking up on someone in a noisy environment is trivial if they're not taking care to watch all approach paths, but presumably good sentries know to do this; maybe they can use the better of Per or Soldier to notice infiltrators using Stealth?

It seems the hardest part for would-be ninjas isn't reaching the target or killing him quietly, but keeping him from making more noise than the kill attempt; you have to kill him in a way that keeps him from calling for help or screaming, keeps him from thrashing around too much, keeps him from hitting any big red buttons, keeps him from sending a radio signal, and keeps him from making a noisy thud as he falls. Of course if you're just moving fast and shooting people on the way in then it's not an issue if the guards make a little noise when they die (because you're already making that much noise anyway) and shooting is a much safer, easier, and more effective way to attack people than futzing around with extreme levels of Stealth and grapple/stab/stab/stab attempts.

Also, there's a question of deniability and intel here. The more exotic your tools and tactics, the more obvious it is that you're working for someone with a lot of money and access and the ability to train ninjas, and it may even be obvious who you're working for. But if you just shoot your way in, using relatively common weapons and ammo, it's not obvious who you were and you might have been working for almost anybody. Alternately, false flagging is possible here, if you have the ability to adopt the tools and methods of the guys you want to frame.