The Wireless IntelliMouse Explorer that is.
I've been using a lot of Microsoft mice over the years so when I saw that Tilt Wheel technology, I thought that I would use it as much as the Scroll Wheel one: a lot! Well, it turns out I don't.
But the mouse shape and the Scroll Wheel feel so perfect! Too bad the Forward Internet Button is not on the right as it is on the IntelliMouse Optical, I end up not using it.
For kids and laptop use, I still love the Notebook Optical Mouse.