Just to add my two cents, I have played around with Doug's RSK Mk5 from CRKT and I am pretty impressed. It seems a lot more substantial than a cheap folder and is flat enough to take up little space. It is usually*** my EDC backup in the bottom of an Altoids tin first aid kit. As has been discussed elsewhere on this site, like many I found the sheath not to be secure enough, but that is a known issue and I am waiting for the promised replacement from CRKT. For the price, I would certainly recommend the knife.

***I am currently working in a situation where I go back and forth through security so I am not carrying anything EDC and I miss it. :-(