I will try to post a photo of my "gear" tomorrow, but to be honest, I don't yet have a bag. Could be because I haven't done 100's of caches (though I've just hit 100!), and could be the caches I've done are relatively easy ones really.
My gear generally stays in the car if we aren't going far, but will join me in either a light jackets front pouch pocket (that act's as a bag tied round my waist if needed!), a backpack, a hydration bag (for a literal caching run), or a pocket/lanyard.
My gear list in a general order of importance (note this is an allergy friendly kit as i need it!):
GPS - Garmin GPSmap 76cx (my new toy only a week in my hands old (second hand))
Ipod - 8gb nano in a case. I use GSAK to put the caches on it.
Lanyard that the ipod and gps carabinas onto.
Pencil - To write on those pen missing/wet paper caches
Hayfever/Allergy pills/sprays/drops (had itchy bites, and very severe (eyes swell shut anyone?) hayfever whilst caching)
Asthma inhaler (had a asthma attack on the hunt!)
Itchy bite cream (Being allergic to grass does NOT work with caching!)
Geocoins that I've picked up recently and I'm needing to move on
Any trade items that I want with me - just in case
Zip lock bag (it's small) to pickup junk out of caches that doesn't deserve to be there.
CITO bags (at times)
Generally it's a mix of what I think would be good at the time. If I'm hiking/tramping it's less trades and more of tents, foods etc. If I'm just going 10 metres, it's often only the GPS, if that even!