Going from memory:

( way back when I used to keep an appropriate freewheel tool in the seat bag in case I broke a drive-side spoke or three )

1. tire patches ( used to have matches from back when things were done that way by some )
2. tire levers
3. 15mm stubby wrench ( or a Surly Jethro Tool, or both, or neither depending upon which bike I'm on or where I'm going)
4. Multi-tool (currently a Topeak Alien II)
5. Small crescent wrench or small vice grips or small channel lock pliers or needle nose pliers or bent nose needle nose pliwrs or wire cutters, or some combonation of those or none of those.
6. CO2 inflator and one to three spare cartridges.
7. Sometimes a mini-pump, sometimes a frame pump, sometimes a Road Morph pump, sometimes just the CO2.
8. Tire boot patches.
9. Sometimes spare batteries for blinkoes and lights
10. Short sections of old tires with the beads cut off to be used for those rare times that a normal tire booting just won't work. Read about it in an old magazine article 10-20 years ago, never needed to do it, but still have the tire sections in the pouch.
11. Ink pen and some paper.
12. other stuff

I'm thinking I'll maybe get the bag and take a picture off all the junk currently in it and the extra stuff I sometimes carry.