Batteries for loader and Marker, at least a couple spare. Box of ten Duracell 9v from ebay for about £8.50.
Allen Keys for your marker - ball ended metric and imperial set.
O-ring kit for your marker, not just a random set of markers.
Spare screws for your marker, they tend to get dropped in the muck and grass if you've to take your marker apart.
Spare ASA
Printed manual
Macroline and elbows if required
Burst discs
Screwdrivers are handy to have, some markers have philips head screws in the grips plus they can be used to poke things.
Lube (oil and grease) DO NOT put oil on your ASA threads, shouldn't need it plus it's dangerous. Clean the threads with a wet wipe or tissue.
Spare bolt if you're not shooting a spoolie ie ego bolt or whatever.
Spanner for burst discs, spanner to fit elbows.
Electrical tape.
Zip/cable ties.
Cotton buds
Small multitool can be useful
Small flashlight for early morning winter starts or better a small headlamp.
While you should be prepared to sort your own marker out it's nice if you can help others when they're stuck. Don't let it get to the stage where you turn up and get handed a marker to fix as soon as someone sees you, I did and it pretty much caused me to stop turning up some days. Be nice, don't be too nice. Have enough tools to sort yourself but don't carry orings for everyone on your team. If you're giving out batteries make sure you get paid for them, even if it's only a quid.
At the end of the day where do you stop? You can have spare solenoids and all that but you'll not always have the same marker, I've never had to fit a new solenoid to my marker. The above list should cover you for most common problems. Best thing you can do is know how your marker works.
Some other nice things to have in your kitbag
Spare mask lens
Wet wipes
microfibre sports towel
toilet roll/tissue packs
heavy duty black bin bag for putting manky gear in, your car or your lift will thank you.
spare dry socks and boxers and t-shirt (all can be stuffed in a single pod)
talcum powder
snack bars/drinks
deodorant
spare emergency money for a taxi/hot meal/phone calls £10-20 should be enough to get you out of a pinch. I also have a list of phone numbers in case my phone gets nicked or lost.
small digital camera
It looks like a lot but most of that stuff will fit in two pods.
