There are alot of good ideas mentioned here already. Kershaw, Benchmade, and Spyderco all offer small EDC type knives. In the Spydie line I might suggest that you consider the new Native w/Spyder edge. I have a plain edge Native in S30V steel and think its a great buy for what you get. I am just not the biggest fan of FRN handles, but the blade is very nice. Look at newgraham.com for a nice buy.
For a very small EDC I like the Benchmite for business or church attire. The Native is my other "small" EDC type user. Beyond that I really prefer my type III Strider SNG or Spydie Military. The 3 to 4 inch blade is just better for me.