String wipes...errr no. A touch of rubbing aclohol works for me.
Pick grips...Yes! I was dropping picks due to fatigue during the gig. Especially those tiny jazz III things.
Ibby multi-tool. Yes, yes, yes. Great thing, used one. Super useful. They do stock locally.
Case freshener. No. Just no.
Ax handler. No. That's what couches are for.
Contact Cleaner. Yes! Not sure how this is a accessory though.
Guitar Polish & Conditioner. I've mixed results with various brands, prefer other options.
Microfibre cloth. Hell Yes!
Cables. Hmm, can't help but say he's sponsored by Hosa.
Capo : If you need one.
Other things :
PSU daisy chain for powering multiple pedals off one psu. You'd be surprised how many cheap psu's are just a case to hide this arrangement. (E.g. Power Bank).
Pick holder - That dorky spring loaded thing, I've got two stuck behind headstocks, I think they're great, likely I'm the only person!
Egg timer - great for time boxing 5-15 min sessions. A app would work too, but I like the timer.
A cordless drill (low voltage) with a string winder attachment. More useful than I could tell you!
A bottle of valve oil - A trick I got from Graham - this is great for lubricating open gear tuners, etc...Just a drop goes a long way and tends not to dry out or work itself into a paste.
Silicone spray/liquid - Amp looking crusty? Guitar case looking tired? This stuff is great for sprucing old vinyl up, I've had great results with the liquid.