First Aid Kit

Every Participant

Mosquito repellent
Malaria prophylaxis
Sunscreen
Mosquito net
Organ donor card, something that states your blood type, and the whole "Who to contact in case of emergency" shebang (there's a page for that in German Vaccination books). If you're hardcore DNR or something, please let the others know.
Your own regular medication and whatever you expect to be needing - lactase tablets, antihistamines, ..

Iberogast: against tummy aches (20 drops in a glass of luke warm water, 3 times/day, sip slowly)
Lorano: Antihistamine (1/day)
Loperamid: against diarrhoea (2 tablets initial dosage, max. 6/day. See doctor on day 3)
Coal tablets: also agains diarrhoe, but milder (2-4 tablets / 3-4 times a day. See doctor on day 3)
Malarone: Stand-by malaria medication (EMERGENCY ONLY! If you can, see a doctor before taking them!!)
Aspirin/ASA: for blood thinning, in case someone's blood doesn't agree with all the flying (do not use ASA as a pain killer in the tropics, for exactly that blood thinning reason)
Paracetamol: Pain killer and against fever (initial dosage: 2 tablets, max. 8/day)
Doxycycline: Antibiotic

Antifungol: against fungal skin infections (apply once daily and again after shower)
Kytta-Balsam: aching muscles, contusions, sprains
Voltaren: same, but tougher. Contains Dicolfenac (anti-inflammatory drug)
Vomex: against sea/air/travel sickness (1 before trip)

CPR Shield
Gloves - 2 pairs
Emergency blanket
Disposable needles and syringes: 4x5ml, 2x2ml (We should not need those, unless something really bad happens somewhere really off the beaten track. I can't imagine this, but Murphy says if I don't bring them, it will happen.)