Some things you might find usefull:
Ball starter
Nipple dispenser
Nipple cleaner (I use an acetylene torch tip cleaner, it's cheap and works)
Extra nipples
Speed loaders
A good powder measure (preferably 5 grain increments or less)
Cleaning jag that fits the threads on your ramrod
If you must use a brush to clean (not always necessary); again make sure the threads allow you to attach to your ramrod. This saves you from packing an entire cleaning kit with you.
I'm sure I missed something. Seems like I pack way too much crap around when muzzy hunting.