I play Beach Ultimate 2-3 times per week. I don't want to think about what I need to take each time, so I take everything! Of course the standard shorts, dark and light shirts, a hoodie, and sweatpants, but there is a lot more!

Beer glove - I hate warm beer
Beer opener - Duh!
BULA badge - To give to special people
Cold spray - Sprain anyone?
Cones - Always bring!
Disc - Go figure
Garbage bag - Extremely useful when it starts to rain
Hackysack - Timeout material
Hat & Gloves - It does get cold sometimes
Holy Seat - For those dirty toilet seats
Pen - To help me remember
Powerbar, Dextrose, Gatorade - Anything to help my old body
Sandskins - Like Sandsocks but better
SAS survival guide - I don't know why
Sunblock - Of course!
Swiss Army knife - Because you never know...
Tabasco (mini) - I like my food spicy
Towel - The sea is always tempting
Visor - Get the sun out
Water battle - For when there is no beer
WFDF Rules - Don't leave home without them

I think I am covered... :-) Or did I forget something?