Softballs. For obvious reasons.

Grass stains: optional (Source).

Fastpitch bat. Specifications differ depending on programs.

Fastpitch glove. Please don't try catching a softball without one of these.

If you're a catcher, a catcher's glove, which looks less like a glove and more like a basket.

Cleats. Running from first to second base in Converse shoes is not a good idea.

Uniform, which consists of pants, belts, socks, shirts, and a baseball cap. And no, you will not be required to play ball in tiny skirts like Madonna in A League of Their Own.

Slider shorts (not unlike bike shorts), for maximum movability.

The shinier, the better.

Batting gloves, so you can stall at the plate while fastening and unfastening them, clapping them together, or spitting in them.

Batting helmet. Again, for obvious reasons.

Catching helmet (picture the facemask put on Hannibal Lecter in The Silence of the Lambs).

Other protective gear, such as chest guards and shin guards. Seriously, protect yourself.