I just got a new Logitech I-Feel Mouse. It's... interesting.

The key point of this mouse, aside from being a really nice USB optical mouse, is that it can let you "feel" Windows.

Yes, now you too can feel the SLIME that windows REALLY is. (j/k)

This feedback is not tactile in the sense of "I feel it in my fingertips," but more like bumps or short vibrations, depending on the theme you have. One feels like you're scrolling the wheel, with short bumps. Others make it feel like a toy that just vibrates softly. One makes it feel like there's crap on your desk (I don't like that one).

The feedback is provided by a small motor contained in the mouse. It's fired whenever you pass over a GUI Object, such as a button, a menu item, hyperlinks, icons, window borders, anything that is a standard Win32 GUI object (which means it doesn't work with anything nonstandard, like mIRC buttons, or the buttons in AIM).

Unfortunately, this doesn't affect the motion of the mouse, so you don't get cool springy action when dragging things, but it does add another (if a bit annoying) dimension to your mouse. Whee.
As a side note, 30 minutes after I got the mouse, I turned the "feel" feature off. I haven't turned it on since. (ed May 11, 2001)