I've got four available.
The goto is the current onfield cap. 5950, low crown. I wear it all the time, it's well broken in and has the sweat stains to prove its been used.
On occassion when my wife gets completely sick of looking at me in it, I trade it out for the Cooperstown 71-75...the "red cap", or the two seph mentioned in the original post: the '59 Go-Go-Sox cap, and the blue one from the twenties (?).
It breaks your heart. It is designed to break your heart. The game begins in the spring, when everything else begins again, and it blossoms in the summer, filling the afternoons and evenings, and then as soon as the chill rains come, it stops and leaves you to face the fall alone. - A. Bartlett Giamatti