A gearbox with a gear ratio of ten to the power of 169. The last gear will *never* turn once; it’s unlikely to turn even a detectable amount. Not just because there are probably no plans to hook the *first* gear up to a perpetual motion machine, but the fact that mo matter how fast it’s spun, that last gear will succumb to proton decay before it could turn the least bit. never mind the fact that it’s made of plastic and will crumble to dust in less than geological timescales.
Someone will doubtless improve upon this.