the kobold ones were pretty nasty actually as they were poisoned etc iirc?
My suggestion is this:
Caltrops, simple weapon, Int vs Reflex (skill dictates how good they are).
Damage:1 (they aren't that lethal!), and Slowed (save ends).
but can treat square as hindering terrain (takes 3 squares to move through without harm)
bag of caltrops 1lb fillls a close blast 2 (10'x10') area
Huge and some other creatures (common sense!) are immune to them.
Charging creatures make a secondary attack on them, fail = they fall prone and suffer further 1d4 damage.
caltrops are not about killing...it' about tactics...unless you use poison!