Bolivia
If you travel a month, it is likely you will catch a new strain of a cold, possibly experience travelers diarrhea, be injured, and if boats are involved experience motion sickness. If at altitude, experience altitude sickness. So here's my travel pharmacy, buried at the bottom of my suitcase. Cipro, Airborne Vitamin C, Zinc lozenges, Mucinex decongestant, Immodium and Pepto Bismal, Diamox, Ibuprofen (600 mg), Hydrocodone, Oxycodone, Stugeron. For injuries, Bacitracin and ace bandages and tea bags (clotting agent). Finally sunscreen, insect repellent, and camp suds. Most of this you'll never need, but if you need it, you'll need it bad.
Packing II - The Rest of the Kit
And here's the rest of the kit. Scuba mask, fins and snorkel would depend on where you're going. And since we'd be at 13,500 altitude on poor roads and trails, waterproof jacket and boots were helpful. And it all fit nicely in my Eagle Creek rolling duffel from RUI.