I used to not carry anything, then I had a flat that I tried to ride back on. Less then 5 miles later, the tire was coming apart, and started to trash my rim. After that, I carried a tube and tools to fix it. From that point, anytime something goes wrong on the trail, my carry along list grows. Well, pictured below, is what the list has grown to, and it all goes into the Ogio vest:
15mm/17mm open end
8, 10, 12 mm combo wrenches
Wire cutters
vise grips
phillips screw driver w/ duct tape on shank
multi purpose tool
12" crescent wrench
Allen combo tool
Knife
2 sizes of zip ties
Epoxy kit w/ mix sticks
Spare front break lever
Spare clutch lever
Spare shift lever
chain breaker
2 master links, and small piece of chain
Axle nut spoons
inflator kit
patches tire gauge
valve core tool
soap
Front tube (you can use a 21" in the rear too)
Tow strap set up (1 over the seat peg to peg, the other to connect bikes)
Work gloves
Rags
Not shown:
phone
70 oz. bladder
sun glasses
camera
protien bars x2
5 hour energy drink
and safety meeting items
I also sometimes carry a small backpack in addition to the flight vest with:
Jerky
A sandwhich
and 4 iced beers
This is only for a all day in the saddle ride, with no eating establishment in the agenda.