I was checking out the Topeak Alien DX multitool. I like this one because it has a pair of pliers with wire cutters built in and pretty much every other tool there is. Also has a blade.
http://www.topeak.com/products/Tools/ALiEN_DXThis Topeak PropShock Pump looks like a great thing to have just in case the air shock goes, it can be turned into an emergency rigid replacement. Pretty light too compared to other shock pumps.
http://www.topeak.com/products/Mini-Pumps/PropShockSpare Der. hanger. There's also this emergency der. hanger from Wheels Manufacturing.
Spare spokes.
Hypercracker cassette locking remover.
Spare suspension pivots and bolts, spare stem and seatpost bolts, spare chainring bolts, rotor bolts.
Tube and tire boots. Stans sealant. C02 for seating bead.
Shimano plastic tool for removing crank end cap.
19mm cone wrench...my pivot bolt nuts...
Maybe I'll drill holes in the arm and cut it down for weigh savings. Maybe custom Aluminum one made? Titanium?
Spare brake pads, der cables. Brake bleed kit? Spare Brake hose and barbs/olives?
Spare chain links, quick links, pins.