Let's see if I can help a fellow Scout out...
I used to own the Victorinox one-hand trekker. It fits your criteria pretty well except for toughness-as to that, if you take care of it you should be fine.
The blade is partially serrated. Imagine a standard combo-edge blade in reverse; the near one-third of the blade is plain, the rest is serrated. The serrations look like a wave, sortof. They offer enough increased power to make short work of fibrous material, but they can probably be sharpened a lot more easily than, say, Cold Steel. The blade is a left-handed liner lock, which means that if you're a righty you pull on the liner, rather than push. All in all it served me very well. I found the serration style nice for whittling, since there's more control over the tang end of the blade. The other tools include a can opener, bottle opener, punch, screwdriver and saw. The saw has little bits of metal filings on it that come off with the first use and leave wicked sharp teeth. The blade has play up and down.
I carry a Spyderco Delica 4 combo-edge. It looks more weapon-like than the SAK, but the blade is an upgrade in almost all areas. Better steel, better NIB sharpness, better HT,
easier one-handed opening, better ergos, more grippy, tougher. I'd say you can't go wrong with that. If you want bigger, there's the Endura.
The Spyderco Manix2, if you can find one, is a steal. I don't have one, but here's what it has going for it:
Absolutely solid lock.Ambidextrous too.
Built like a tank.
Strong blade that's a good shallow slicer (hollow ground)
Nice ergos.
Built like a tank.
Less expensive but still premium steel.
You probably can't go wrong.
Lastly you should take a look at the Byrd Wings. Nice design, and a bit more versatile than a CE blade. Cheaper too.
YIS
KI