In the past, I've carried a CRKT PECK, Kershaw Two-Can, SOG Flash I, Boker Credit Card, Leatherman Style, Leatherman Style PS, and Spyderco Squeak.
The 1.0 oz. PECK was nice, one-hand opener, like having a heavy-duty razorblade in my pocket. Nice and sturdy frame-lock, but a bit heavy for what it is.
The 0.6 oz. Two-Can is a sleeper. Clever scissors and knife with only two blades, it always catches my eye before every backpacking trip because of its weight. Terrible carabiner design though, and I prefer knives that open with one hand.
The 1.2 oz. SOG Flash I is super-nice in the pocket. Good steel, nice handle, small package, assisted opener (thus "flash").
The 1.2 oz. Boker Credit Card is an interesting frame lock about the size of the credit card. It is a bit harsh in the hand for heavy cutting, but is wonderfully slim on the pocket (even with the pocket clip).
The 0.8 oz. Style is my daily EDC multi-tool. Sadly, this now has replaced my Style PS (see below).
The 1.6 oz. Style PS is a wonderful compact multi-tool positioned for airline carry since it has no blades. I found the pliers (same as Squirt P4) quite useful, and the scissors could be opened with one hand (somewhat easily). Unfortunately, the scissors broke three times while in my pocket, and although Leatherman replaced them twice, I'm afraid it'll just happen again.
The 1.2 Spyderco Squeak is the EDC knife I carry when not using the Style. It has a clever non-locking blade that can't collapse because your finger blocks (in a safe way) the blade. Wonderful steel (Italian!) and solid handle for a small knife.
I have carried by accident an Opinel No. 7 and a Kuhn Rikon Paring knife in my backpack, along with a Leatherman P4, in addition to my EDC!
The PECK, Flash I, and Boker, can no longer be "legally" carried here in NYC because they have locking blades, but then it depends what you're doing when frisked. I still carry them now-and-then, but shhhhh, don't tell anyone!