I was looking at Justin8649's Gallade analysis just now, and I noticed that Shadow Sneak did not get a mention, even in the responses. I suppose this is due to it's low power that doesn't receive STAB, but I have always used Shadow Sneak on my Gallade rather than Night Slash. It needs a Swords Dance to rack up a good amount of power, but I think Shadow Sneak's merit's outweigh Night Slash's. It allows you to get the jump on many fast Pokemon Close Combat wouldn't destroy: Alakazam, Azelf, CS Gengar, etc. By using Shadow Sneak instead of Night Slash, you can get in a free Swords Dance more easily rather than having to predict their switch in to Night Slash/Thunder Wave them. Thunder Waving an Alakazam with Synch would screw you over anyway, but unless you take it out with Night Slash on the switch-in, Alakazam is going to get in a free Shadow Ball on Gallade, which can hurt. Trying to Thunder Wave CS Gengar doesn't work too well either. I'm not sure about this, but CS max Speed Timid Gengar would still be pretty dern fast even if it's paralyzed, at least compared to Gallade. And if you mispredict and don't Night Slash Gengar on the switch, you pretty much have to pull Gallade out of there and sacrifice any Swords Dance you might've gotten in. Having a priority attack is a good way to take out weakened Choice Scarfers in general. Gallade doesn't like eating Azelf's Shadow Balls/Explosions either. With Shadow Sneak, you don't have to worry about any of this really. You could even do away with Thunder Wave altogether and have WoW instead as a way to mess up strong physical Pokemon that would KO Gallade, but you'll sacrifice SS's power if you don't have Swords Dance. Shadow Sneak is also a good way to take out other Gallades that could have more Speed EVs than you.
I believe one of the main reasons people put Night Slash on Gallade is for Dusknoir. However, a Shadow Sneak from max Atk Adamant Gallade after a SD 2HKOs Dusknoir, taking out somewhere close to 3/4's of it's HP. Gallade's Shadow Sneak outruns Dusknoir's Shadow Sneak anyway. The only real drawbacks I see from using SS over NS are that Normals are immune to it, it has less power, and it doesn't have the high crit rate. Most normals aren't going to switch in on something with Close Combat anyway, and the decreased power isn't going to matter so much against those key Pokemon I mentioned above, except Dusknoir. I might be overlooking something here, but it seems to me that Shadow Sneak should at least get a mention as a smart alternative to Night Slash on Gallade.
I believe one of the main reasons people put Night Slash on Gallade is for Dusknoir. However, a Shadow Sneak from max Atk Adamant Gallade after a SD 2HKOs Dusknoir, taking out somewhere close to 3/4's of it's HP. Gallade's Shadow Sneak outruns Dusknoir's Shadow Sneak anyway. The only real drawbacks I see from using SS over NS are that Normals are immune to it, it has less power, and it doesn't have the high crit rate. Most normals aren't going to switch in on something with Close Combat anyway, and the decreased power isn't going to matter so much against those key Pokemon I mentioned above, except Dusknoir. I might be overlooking something here, but it seems to me that Shadow Sneak should at least get a mention as a smart alternative to Night Slash on Gallade.