Small coffee thermos
Winter gloves (for walking between shots)
Heavy lined sweater and lined rain pants

Hand warmers are always good.

Titleist mittens hand warmers and a winter hat are a must. You also should always bring an extra layer

I have a pair of insulated pants made with synthetic material that were originally designed for hiking that I've found work better than any traditional cold weather golf slacks when the temps dip into the 40's. They're warm and wind & rain resistant. Add a winter cap, long-sleeve base layer, and additional layers as needed, and I'm good to go.

All depends on how cold it is. Lip balm a must. Layers of clothing. A hat or winter cap. Cart mitts. Water to stay hydrated ( the cold weather will dehydrate you). Maybe even move up to a different set of tees considering the ball won't carry as far.

Warm socks, mittens, and waterproof shoes. Take care of the hands and feet!

Airline tickets! We get a lot of winter visitors in San Diego. :)

A calendar so I know when spring returns