Jewelry should never be worn. They can cause injury to you or another player, besides getting bent or lost. So leave these things at home or locked up.

Bases should be properly set into the ground so that no edges are turned up to minimize tripping and sliding injuries.

Don't forget the sunscreen. It should be part of every player's standard equipment, even if it's a cloudy day because skin damaging rays aren't blocked by an overcast sky.

Finally, special safety equipment makes sense for specific positions. Like sunglasses for fielders and in fast pitch and junior olympic play, face masks and chest protectors for catchers.