This is the smallest form Johann has access to - and it is sponsored; it's not clear if he could manage quite this dramatic a size reduction entirely on his own power.  The sponsor is a slightly-summer-aligned-but-mostly-wyld-fae named Kiriik (who Johann assisted in dealing with a logging operation); her normal form resembles a ptychozoon kuhli (look it up on wikipedia) - except with two heads, which results in her tending to refer to herself in the plural.  She is also highly venomous - a trait that Johann's copy shares, but real geckos do not.  (Technically, Kiriik _can_ assume an at least mostly human form; she just prefers not to, complaining that having only two eyes is "disorienting; we don't understand how you humans manage.")

-1 echoes of the beast (chameleon skin - can use stealth skill without penalty due to lack of cover, though trying to blend in with a transparent or reflective surface won't work so well.  On the flip side, Johann tends to rely on this ability when it's present - resulting in aspects like "thermographic goggles" being usable to compel total failure of stealth instead of just providing bonuses to perception.)
-1 diminutive size
-1 sticky toes & gliding flaps (this provides a bit more locomotive ability than just spider climb - but less than full on flight, so I figure it's still just one point of refresh)
-2 inhuman speed
-4 supernatural recovery
+3 catch
-1 claws (this is actually just a fast acting but relatively weak poison; the weapon rating does not apply to non-living targets)
-2 venomous
-1 variable poison - the general effects of the poison can be chosen at time of application and can range from harmless itching and cosmetic damage, to psychotropic effects, to non-lethal paralysis / narcolepsy, to full out lethal necrosis.  This does not change the mechanics of the venomous power, merely the allowable range of take-out results.  (Kiriik's favorite lethal venom results in flowers growing out of the victim; sadly, this is something of a magical effect and Johann has been unable to duplicate it.)

(unspent: +1)
+6: fists, athletics
+5: stealth, alertness
+4: lore, investigation
+3: conviction, scholarship, empathy
+2: discipline, endurance, rapport, survival
+1: presence, deceit, performance, might

details on individual forms:
One male gecko; looks like a perfectly ordinary kuhl's flying gecko.  As this form is sponsored, the available options are limited by what Kiriik chooses to provide; Johann has tried to assemble other gecko forms, but hasn't gotten any working yet.  As with any sponsored form, Kiriik is aware of when Johann uses this form and - depending on her mood - may choose to show up and make a nuisance of herself.

Other notes:
The poison generated by this form is highly volatile - as in, it decays rapidly and is difficult to store without losing potency.  Johann *can* manage to keep a dose or two around, however - by using the normal rules for magical potions.
Also, this form does not confer any particular immunity to conventional venoms - it's immune to its own poison, of course, but even if Johann mimics the effect of, say, rattlesnake venom, this would confer no protection against an actual rattlesnake.