Quick Attack is definitely the best special.
You now can't be cornered, can set up into combos from any aerials [and possibly ground moves], if you read an airdodge at mid percents you get a free smash attack (which can kill depending on location etc.) [due to landing lag on airdodge], recover from almost anywhere so you can go basically as deep as you want, and you can ALWAYS mixup recovery angles, while it's good enough to get onstage or to ledge from a ledge trump leaving you with mixups even then. It's also easy to get from the ledge to center stage so that you should rarely be stuck on the ledge. You can also get anywhere you want on Battlefield in less than a second, and anywhere on the base of most stages in a second or less as well, making covering landings MUCH easier. And it combos even better on any stage with slopes or moving platforms.
Oh, and while it's wholly irrelevant to regular games, second hit kills in sudden death. If you enjoy salt, get to sudden death, kill them with it [really easy since it's so safe], and watch the salt fly.
Might be better than Sheik fair, since Sheik fair does maybe half of that stuff yet can just be used in neutral a gazillion times rather safely, but I'm not gonna spend a bunch of time arguing about a topic like this.