On the small side, there's the Esee Candiru. Disappears in pocket when standard with out handles. But more functional with the optional Micarta handles.
Or in the mid-size, the Esee Izula or Izula II. Same blade, but the Izula has a slightly smaller grip, and handles are optional. The II comes standard with Micarta, and a bit bigger grip. Sorry, don't have a good pic of either of these.
On the budget side, the Schrade SCHF5N. Not fancy, but gets the job done....and cheap.
In the super micro realm, the Boker Gnome, or even smaller Toucan.
Ultra thin and light, the Spyderco ARK. More of a last resort defensive blade, not really built for utility. Knife if around or under 1 oz. I think the sheath actually weighs more. Sorry again for another crappy pic, just what I had available. It's the small fixed right in the middle.
Found a pic with the Izula II. Also last recommendation, but actually one of my favorites...the Boker Fitz (this one in Stag). Lower right in this pic.
Doh! One more, a little off the wall.

If the fixed blade will be used mostly for lunchtime food, take a look at the Boker San-You-Go (on the bottom in this pic). A pocket sized Santoku. Comes with a leather sleeve with retention strap, but no belt loop. What a great food slicer.
Really should add the edge pic when showing the above. These three all look similar in size, but when you see the stock thickness, it's easier to see that they are nothing alike. The San-You-Go in the middle has a much thinner blade material, with full flat grind as a chef's knife. The other two are very heavy utility blades.