We live a long way from town, so we've got a pretty well stocked area in the cold room for treating stock.
Biomycin, Nuflor, LA200, Micotil (dangerous stuff but very effective), Revibe (electrolytes), Calf Start (powdered colostrum...never hurts to have some), Coccidiousis boluses, E. Coli boluses, Amprol, Spectam, etc.
Also have fiberglass casting material and padding on hand in case I have to set a broken legged calf (run dehorning wire underneath when you set the leg, makes it easier to saw off the cast when you remove it...and NEVER set it too snug...you run the risk of cutting off the circulation and the calf will get gangrene in the leg).
Then of course there's the selenium for white muscle disease, but like the electrolytes and colostrum, not a medicine, per se. Oh, and calcium in case need to give a cow a shot. Haven't yet, but better safe than sorry and it's cheap like borscht. Bloat Eze too, but haven't had to use that in a long while. Oxytocin is marvelous stuff, and also inexpensive. Also have a couple shots of Lutelytes.
Also never hurts to have a long curved needle and some suturing tape (not sure what the proper terminology is ...Vicki would know) for sewing up a prolapse. Again, not meds but handy all the same.
Take care.