Extra syringes, it's a PITA to need one now when the feed store is closed. Useful not only for injections, but feeding small amounts of liquid, or dispensing small amounts of medicine/dewormer/etc
Super small sharp scissors are handy, the kind I use are sewing/embroidery scissors and I have a pair for humans in the bathroom and a pair for pets in the kit
I would like to get some vet scalpels to keep on hand for when you need a super sharp skin knife.
I probably have a list of ointments a mile long
Epsom salts are one of the handiest things to have on hand too, for humans and pets
bandage supplies, gauze, vet wrap, cloth medical tape, butterfly suture strips, duct tape is always good
make sure to have a heating pad and heat lamp that can be used for the weak (for example, my mom would demand we have two heating pads one for humans one for birds, but I just have one myself)
I also keep my dog's nail clippers, a few cheap disposable razors (used in the past to shave a dog's sore), the legbands and pliars, and the Frontline meds in with all this stuff as well just so it's all together.
I don't have any oral "meds" exactly, but I have rooster booster vitamin supplement, and the non-iron Poly-vi-sol, again it's kinda a pain if you have to run out to
WalMart at 2am to get baby vitamins (speaking from experience here)