This basic list is pretty comprehensive and will cover most "normal" shooting situations. There are sports and situations though were other gear is useful, so here's a "nice to have but not required" list:
- extreme wide angle zoom 12-24 (good for Xtreme sports and other circumstances where the photographer can get close enough to use such a lens)
- underwater camera housing for surf and other water based sports
- remote camera control (for rigging a remote camera on a backboard or some other location)
- camera stand or clamp for remote setup
- extra flash units and wireless triggers
- sports camera strap such as the Black Rapid RS-4 for a second "shoot from the hip" camera
- camera raincoat for shooting in bad weather
- camera beltpack (useful for traveling light and moving quickly)
Another useful item for sports photography is the camera vest. While this is a bit of a special use item, it makes life a lot easier for the sports photographer because he or she can move faster and more easily than when toting a heavy camera bag. Camera vests also tend to distribute weight more evenly, putting less strain on the shoulders and back.