Recently I picked up a couple of Xonox double-ender cartridges on my weekly garage sale hunting. They aren't unusually rare or anything, but they are really cool, and for their time, where pretty useful (Well, if the games on them didn't suck.)

It got me thinking, however... that design could have been really useful for many things.
During the N64's life-time a lot of high profile games went over to the PS1 rather then stick with the N64 due to space limitations of cartridges. If they had mad a similar cartridge to the Xonox double-enders, just also having the same memory linked between the two ends, space capacity for games could have doubled possibly allowing more room for longer and/or more graphically advanced games. This could have also worked for other systems. Something like, say, re-releasing games that had a squeal both on the same cartridge in the lifetime of the system.

I don't know... maybe I am thinking to much about this, but I just think double ended cartridges where a really clever idea.