A. Well, a big bird needs a big toy, and a small bird, a small toy. If you give the bird the wrong-sized toy, injury is possible. Most toys are labeled for small, medium, large, and extra-large birds. A. Depends on the bird. Some love bells, some like twirly, spinning toys, some like rawhide leather to chew on.
Wood is a good choice for any bird, it exercises the beak.
Fabric is excellent for feather-pluckers. The bird should have a variety of toys, but only two or so in the cage at a time. Rotate the toys about every two to three weeks so the bird doesn't get bored. A. Birds can be taught to do behaviors such as basketball, roller skating etc. While all species can be taught successfully, individuals may vary in their willingness to learn.