Be prepared for all emergencies. Many of these are vital, I did not include very many medications and hardware that may come in handy once in a while, or never. I have use all these at some time or another.

MEDS
Melafix
Pimafix
Ich-treating medication containing either malachite green or copper
Maracyn 1 & 2
Triple Sulfa
Jungle Life-guard
Prime

OTHER
Salt
Clove oil (eugenal)
Water testing kit, complete with: Ammonia (NH3), Nitrite (NO2), Nitrate (NO3), pH, Phosphate, Hardness (gh), alkalinity (kh).
Activated carbon
Hospital Aquarium
Spare heater

thankfully, I haven't had too many health-related problems with my fish. I've got a few medications knocking around, such asm melafix and a half empty box of octozin. I think it's worth pointing out that medications do you have a shelf life. So be careful about using stuff that may be very old, I personally only buy stuff when I need it, the shop is only couple of miles away.

Not to many close shops for me