Here's my list:

PB Superflash rear light.
PB Big Buddy saddle bag with tire levers (integral patch kit in the levers).
Extra inner tube.
REI Novara Traditional Patch Kit (with tube of glue). I keep $5 and some change in the same little kit box (nice to have it it as a boot or in case you just really need to buy some snack or drink).
Multi-tool (Topeak Hexus II).
Pair of vinyl disposable gloves (wonderful to have if you have to repair a flat on the rear tire).
Topeak Road Morph G pump attached the the optional bottle cage side-mount.
PB Blaze 2 watt headlight (I don't ride after dark, so this is bright enough for me and the flash feature keeps me visible when in traffic).
RackTime Rear Rack with spring-loaded clamp. I often have a bungee cord wrapped around the frame of the rack just in case.
I have a trunk bag from REI that I got on sale for under $20 that attaches with velcro (it's on the bike only when I think I'll need it).
I have an Axiom Power Bag 2 to hold snacks and phone, but it's on the bike only when I need it.
Oh, and a set of SKS P45 fenders, since I don't mind riding when roads are wet.

I'm a bit "fredly" riding around, but it works for me.