I carry a tubeless puncture repair kit, some duct tape, a philips screwdriver, 2 T type allen keys, a few spanners and a shifter.

On top of that I carry a mobile phone, an RACV roadside assistance card (that covers bikes as well as cars) and a I normally throw a bottle of water in the pannier if it's summer and I'm riding by myself.

 A torch is the first thing I put in my tool bag, then the fuses and multitool

 If ya after the best, I haven't seen any better than the Snap-On Cycleset.

Not easy to come by cheap, but they do appear on flea bay every now and then.

The web site also gives a list of items included for some ideas.

buy1.snapon.com/catalog/item.asp

 Definatly the puncture repair kit, [ mines out of an ARB kit ] The hd air pump. works well and small. Couple of small tyre levers and a spare tube for the front wheel. C type plier for front wheel bead. and 2 rim protectors. Tube repair kit, If lucky you can patch the tube without removing tyre  and tube completely from rim, Then the stanard rest, fuses, shifter ect oh and a little bottle of loctite 343.

 Mobile phone, credit card...

Me thinks me need to have a better look...

A small shifter, Allen key set, (Fucked off the torque screws)  A small straight edge screw driver, 9/16 & 1/2 spaners, my A A A road side pickup sevice card, Mobile phone, insulation tape, a Few differant Zip ties, & a shitload of faith!   

 fuck the tools this is all i carry

 

Hahaha a hammer a shifter and a screw driver. Seriously though I have put a tool roll together, and included a CO2 cartridge tyre inflator with 4 spare charges. I feel though tool kits are becoming a thing of the past nowadays. all vehicles seem to be so reliable now you only need what Will67 said. but back on topic, plug spanners and shifter and a couple of other tools can be handy, all you have to remember is the tools you need on the day will not be in your tool bag.

 In the days when I did huge ks carried spanners , Allen sockets and small ratchet. 4in 1 screw driver and shifter, small gas soldering iron and test light, bit of wire and cable ties..ohh and leather man type tool. Some tube patches and tyre leavers..and one of those emergency cable ends..best $7 I spent.

now, maybe phone, cash and a smoke while I wait for tow truck.