Fixed:
The only real small ones I have actually used to any extent are the ESEE Candiru and the Becker Remora, both of which are pretty tiny and much less capable than - for instance - an ESEE Izula.
The Remora was - in my opinion - a better knife for every day carry when it was offered in stainless steel rather than the current "1095 CroVan" production model.
Between the two, I would give the Candiru the nod right now just because a set of grip scales can easily be bought, and both of these knives need scales if I put very much physical effort into actually cutting with them.
Folding:
Hands down, the Spyderco Dragonfly.