@Lanny brought up some great points in the Found A Jam Band! about being prepared for a gig.
Even if I’m just going down to my neighbor’s house for garage band night, I always have:
So, what’s in your gig bag?
All of what you mentioned +
Strap
Shakers
Kazoo
Tambourine
Truss rod hex key
Sheet music clips for stand
Picks - Just in case
Edited to add Ear Plugs and a Small MP3 recorder
Our illustrious guru @JoshFossgreen discusses what to bring here (It should open right on item 4 of 5 in this video):
Everything you and @Celticstar have suggested plus
A couple of groupies
Bail bondsman number
Hip flask
Small mirror
$100 bill
I would add a set of in ear monitors if you’re going to be playing through the house sound system. Some sound guys don’t want you to use stage monitors, especially in smaller venues.
That’s a big gig-bag. 
Josh’s suggestion of nail clippers is a good one…nothing worse than a hang nail or long nails (if you don’t normally have them) when trying to play
Good idea and maybe an nail file to smooth it out.
Also known as a body bag 
That’s kidnapping!
That’s a terrible thing to call her !
Scott Devine did this excellent video on Gig Bag Essentials awhile back. I saved it in my “watch later” in the hope that someday I’d need it.
Funny story about the Leatherman muti-tool. I was doing a cooking class in Colorado. One of their blenders decided to spectacularly self destruct in the middle of a demo on raspberry coulis (sauce). Yeah, try getting that out of your ear canal, that’s fun.
Out comes the multi-tool. Screwdrivers, wire cutters and pliers to the rescue!
Then the main gas knob on their grill shattered. Again, pliers to the rescue.
At the end of the afternoon, one of the instructors asked why in the world I would have something like that in my knife kit 
Seriously, did you not just watch me salvage your class?
So I have three of them. A big one in my car, a smaller one in my knife roll, and it’s twin in my gig bag. And they have corkscrews 
, you know, just in case.
I also carry a (fully charged) power bank and a couple mini-usb/usb-c cables and my box of picks - just in case - and mostly to let the guitarist try my odd picks 
I buy these sacks of emery boards from Amazon and always keep a few handy wherever I go: in my purse, glove compartment, desk, bass case, etc. They are the best, neatest, and easiest way to maintain your nails. I keep the index and middle finger on my right hand filed down to the fingertips; and if I ever hear my nail catching on a string, I immediately pull out an emery board and give the nails a couple swipes.
Some useful info. I like AMP as a creator, wish he did more
