Well I'll tell you WHAT we had/have had since they've been doing inspections.
We had :
cameras,video and digetal.
Water bottle
Jackets
Squirty fan
Small flashlight
Candy bars
Bandaids!
As far as no nos...a picnic lunch isn't allowed in the park although I have seen people on here write that they have taken soft sided coolers in with some food without any trouble.
The bag checks are looking for weapons or any funky looking electronics that could be a bomb is what I think they're checking for.I know I've seen them have people click their cell phones on and off to varify that it's just a phone.