For most non-designers, the first time they work with a page-layout program, the font list is a playground to them, so their documents tend to be loaded with a painfully high number of fonts. We like to think that more thought was put into the Font Clock, which has different fonts for the hour, minutes, day and date, displayed on those old-skool flippy panels. The clock uses no more than 12 fonts, though from the looks of them, they weren't exactly chosen for how well they mesh together.
Supposedly made to be a 21st century take on the "British 24-hour clock," whatever that is, the Font Clock comes in three sizes, costing $380, $1,075 and $1,580. That makes it a little too pricey for most, but graphic-design firms might go for it, since you can't put a price on being inspired by time.