Well... It largely depends on my mood at the time but I suppose my faves are:
Scope, Shapescape, Marquesas, Funnelweb, and Spectrometer32-128 (is this too many??). This doesn't include those that just make me give out a little giggle as soon as I see them but tend not to leave them on.

A visual I'd really like to see, and one i'm surprised isn't in the car player already (seeing as Hugo et al obviously come from an electronics background and having played with oscilloscopes i'm sure) is a Lissajous visual with the Left channel controlling the x and the Right channel controlling the y. I used to do this when I was a teenager playing with my old valve oscilloscopes. Kept me quiet for hours . Did I read once upon a time on this bbs that there was going to be a visuals API so that third parties could write their own? That would be nice (as long as it was easy ).

Anyway they're my favourites.

beaker
32 gig (various colours)