This is a cat toy ball with a simple design that's quick to print. My first foray into similar toy balls required a lot of support material. This one consists of two domes that friction-fit together with pegs. The size -- slightly smaller than most similar commercially-sold cat toy balls -- and the mostly-closed-off design are loosely based on an existing cat toy that my kitties are partial to, except that one is held with glue, not pegs.
Use it as-is, put a jingle bell inside (as I did -- rescued from a previously stepped on cat toy), or hide a catnip sachet inside (an empty tea bag works well).
For those wanting to get into OpenSCAD, I have included the *.scad source code, although it's not trivial, it's well partitioned into functions, uses reasonable variable/constant names, and isn't too difficult to follow.
Print two domes and one set of pegs. It should be obvious how everything snaps together.
I had great results printing my domes with a raft (though no support, just the raft), no extra shells, and a 25% infill. For the pegs, I used two extra shells and 25% infill, no raft. You will probably have to manually clean up a little bit of extra plastic from where the raft peels away and a bit of drool from the inner apex of the domes.
To go the extra mile, lay out a sheet of 100-grit sandpaper and rub the base of the dome (where it sits on the raft) against it to give it a smooth finish. This will ensure the two domes fit together in the closest possible way with minimal gapping.
Different printers have different tolerances. (There's a tolerance setting in the source code.) If you find it's a bit too tight, you can sand down the pegs slightly. If you find it's a bit too loose, add a drop of superglue to each peg hole. Or just alter the source code and find a tolerance that works best for you.