I have reviewed some keychain/keyring knives a while ago. For non-kc/kr use the list might be somewhat different (e.g., the importance of good clips), but here are my impressions (hope you don't mind me repeating what I've written before):
TRIED AND APPRECIATED
SOG 29 MICRO-DOT; blade 2", plain edge, 440A, high hollow grind; overall length 4.5", length closed 2.6", weight "under 1 oz." (well under, couldn't find the actual data); reliable back-lock, pivot not very tight (after two years use); one-hand opening (right hand, Zytel stud, quite far away from the handle when open, may restrict slicing; Zytel handle, comfortable for 2-3 fingers (the keyring and keys continue from that, with only 1 ring you can easily keep the keys from rattling), surprisingly natural and secure (front) grip (a small finger guard); does not seem to gather pocket-lint too easily; price a bit over $20. This one does not, of course, have a clip.
SPRYDERCO SP28 DRAGONFLY Steel Body; blade length 2.4", edge 1.9", plain or serrated edge (I have both), AUS-8, flat grind, not very sharp before "reprofiling" the edge to Lansky-17 degrees (the plain version, of course); overall 5.4", closed 3.25", quite hefty, 2.25 oz.; very strong back/mid-lock, tight pivot; ambidexterous one-hand opening (hole), easy to open to reverse grip with the ring finger, too; stainless steel handle, polished (slippery, but doesn't get stuck in a pocket or come accidentally out with, e.g., a handkerchief, especially if the clip is removed), provides a variety of grasp positions (none of which very strong with my or my wife's hands), finger choil which overlaps the handle and the blade, very good for accurate work; stainless steel clip (butt-end, not very high) creates a "shelf" to increase leverage while opening; almost immune to pocket-lint, very easy to clean; a bit over $40. For non-kc/kr use, the Zytel version (with an integrated plastic clip) might be a good choice. It's very light and the handle feels even better.
SPYDERCO SP29 CRICKET; blade length 1.9", edge about 1.7", reverse curve with a "parrot's beak" tip, blade thickness 0.07", plain or serrated edge (I have both), blade steel GIN-1/G-2, hollow grind; overall length little over 4.5", closed 2.7", weight 2 oz.; liner lock (tightness varies, my older serrated version is much more precise than the newer plain one; haven't tried the plastic versions), very positive detent when closed (a must for a pocket liner-lock), tight pivot (adjustable); easy one-hand opening (hole), also with the ring-finger (to reverse-grip), but only with the right hand (don't think the other slab/liner can be Dremeled enough); flat black anodized aluminum handle, assembled with PH screws, smooth, oval shape (a bit of "dehorning" and you've got like a smooth, flat stone from the bottom of a mountain river in your pocket), surprisingly strong grip both front- and reverse (I'm not kidding, it surprised me, too); black metal clip on the pivot end (and I mean *end*, removable, fits perfectly to a BM AFCK); gathers somewhat pocket-lint, feels very well in a coins-pocket; between $40 and $50.
Tried but *NOT* appreciated
Benchmade 330 Mel Pardue Gentleman's folder (too light detent, action a bit gritty in my exemplar, right-hand only, not very smooth in shape, though thin, no clip), Boker Gamma liner-lock with ceramic blade (almost nonexistent detent, right-hand only, a horror to resharpen, a bit chubby, no clip), SOG 33 Mini Gentleman's knife (very difficult to open with one hand b/c too narrow hole, though would be ambidexterous, smooth in shape, and small, no clip), Timberline small drop point (rubbish, doesn't even take an edge), Gerber MicroLight LST (simply too small), Gerber UltraLight (no one-hand opening, difficult to get a really good edge, but because of the very secure half-way detent could well be my daughter's first folder when she will be 3). The three last mentioned do not, of course, have a clip.
Some more recent ADDITIONS. Spyderco LadyBug (less than $20) and Baby-Goddard (about $30). I'm sorry, but these would have go to the "tried but NOT appreciated" group (and I gather, you're not seeking anything *this* small). In many ways, they are fine little knives with nice blade profiles, tight pivots, and strong locks (and the Micarta on the BG looks great and smells funny), but the opening holes are simply too small (about 6.5 mm) for my (medium-sized) thumb. The one on the BG is, in addition, so much chamfered that it is virtually unusable. Also, I don't fancy serrations on very small pocket blades. It's much easier to, e.g., sharpen pencils with a plain one. Of these two, I'd prefer the LB. The handle shape of a larger Goddard simply does not function with the size of the BG (as well as the shape of the old Endura on the LB). Maybe the LB could be seen as a "child" of the Endura, so if you carry both, you could say (if needed): "but officer, this little one won't go anywhere without her mother" ;-)
Hope this helps, Jonas. But as Sing advised, do check small folders from (informative) internet dealer sites!
Markku
[This message has been edited by Markku Huttunen (edited 26 February 1999).]