I love these water powered calculators and clocks from Think Geek because I hate buying batteries and get really annoyed when my solar calculator barely works in low light situations (yeah I know, why don't I just move to a better lit room - but that would be too easy). The round clock above is multifunctional with additional alarm, timer and thermometer modes. Just rotate the clock 90 degrees to go from mode to mode. The calculator is a fully functioning calculator with large keys and a 12-digit display. The water clock below even has a place to hold flowers.

If you're thinking what a hassle it would be to have to fill your clock every few days, think again. A full reservoir powers the devices for 2-3 months!