My favorite SAK maker is Victorinox, and it's hard for me to pick a real favorite model, but I'll mention my 3 most-used and favorites. The Classic, Executive, and Tinker. My favorite of the 3 will depend on what use I might have for it...but my favorite to carry is the Executive.
The Victorinox Spartan. I like the fit and finish on the Victorinox better for some inexplicable reason, and the Spartan has all the basics I need without the extra junk that I don't. I am not overly fond of the "pocket toolkit" concept.
Victorinox is Definately the best IMO.I once bought a Wenger SAK just to compare it to the Victorinox,and it sucked.For some reason I could not get the Wenger nearly as sharp as the Victorinox.As far as styles go,that's kind of a personal preference.I'm sure you can find one that will suit you and you really can't go wrong with any of them.I carry a Spartan with the Phillips head option every day at work.I can't imagine anyone using it harder than I do and it is holding up great!
I currently have both, typically I've used Victronix, and don't see much difference so far. For a smaller pattern I like the Victronix Camper, it's a handy set of tools with a corkscrew, and although I wouldn't have bought one myself at the time I'm glad that someone gave me the Champ, with the sheath, compass and such. The Camper and original Leatherman complement one another nicely, as I don't think that any of the multi-tools has a corkscrew.
Smallest: Wenger Esquire, Victorinox Executive. I like the Wenger a little better than the Victorinox Classic because it's about 1/4" longer.
Medium: During the past 20 years I've carried a Climber, a Tinker and now a Spartan with an eyeglass screwdriver in the corkscrew.
Large: Victorinox Ranger. I've never used most of the stuff on it but everyone needs a big SAK.
There is an Explorer model with a saw and the Farmer (Pioneer with a saw) avialible in Europe but is not imported into the USA. there is a Swiss retailer with a website that will ship to the USA, in fact they are often faster than most US based web retailers. They are at www.swiss-knife.com and have the entire Victorinox and Wenger lines of SAK's.