I'm probably extreme on this - at least that's what everyone says. I carry a toolkit that generally contains:
Tools: adj spanner (aka crescent wrench); assorted screwdrivers, allen wrenches (aka allen keys) - metric and imperial sets; tweezers, needlenose pliers; bent needlenose pliers; small files; cutter; shackle wrench; brass regulator tools; dentists' scaler (aka pick); intermediate pressure (IP) gauge;
- Where possible, go for SS. (My stainless steel adj. spanner - made in New Zealand, for yachties - has been with me for almost 20 years.)
Spares and consumables: O-rings; several kinds of o-ring grease; small tube of Christo-Lube (oxygen-safe grease); extra Nikonos strobe bulkhead port; various UltraLite clamp and fitting bolts and other spare bits; tri-glide fasteners (for harness); plastic ties; various lengths of thin nylon cord, kevlar cord, shock cord, surgical tubing, and bicycle inner tube; Neoprene cement (good for more than wetsuite repair); 2-part epoxy glue; duct tape.
Other spares: One extra camera body. Full set of camera housing o-rings. One spare for each regulator hose, one spare 1st stage; one spare 2nd stage; one spare SPG, spare computer, spare mask (prescription). (If I know the boat/operator has good rental/lending gear, I dial back on some of these items. If I'm travelling with a buddy and we using the same gear, the regulator spares are shared.
Some of this gets used by someone (often another diver) on every trip.
You don't want to know about my meds kit.
Frogfish (Robert Delfs)