Here's a top based on Steve Good's rubber band top, but using a pull string. The top stays spinning a surprisingly long time. The handle is 1" birch, the disk is 3/8" x 3" black walnut, and the dowel is 5/16" x 4" long. Finished with Feed n wax.
When it hits the floor, it skitters around like a small animal - fascinating to small kids (and me).
(https://lh3.googleusercontent.com/-Hkr9asElHbM/UhFFf1Hbr5I/AAAAAAAAA2w/jw8FxeTaWN4/w784-h537-no/StringTop.jpg)