It drives me nuts when manufacturers don’t carefully consider how their products are actually used. As an example, I installed a restaurant-style soap dispenser in my bathroom. Why? Due to the flawed design of every single handsoap-dispensing pump bottle on the market. When washing your hands, you 1) wet your hands under running water, 2) start pumping the bottle, then 3) the water from your hands runs down the bottle, collecting around the bottom. After a few times you’ve got a ring on the bottom of the bottle that eventualy turns brown on the porcelain sink top. I got sick of cleaning that ring off, so ditched the bottle altogether and now have a wall-mounted dispenser. A bottle filled with handsoap is supposed to get your hands clean, so it makes no sense to me that it makes your sink top dirty.
Similarly, when cooking dishes that require hand-mixing in the kitchen, I hate having to turn the tap on and getting whatever crap is all over my hands all over the kitchen sink knob. I wash my hands off–then get more crap on them as I turn the water off and touch the knob. (I usually resort to trying to use my elbow, which works about as well as you think it would.)
Addressing this latter need is Delta with their Pilar Touch-Activated Single Handle Pull-Down Kitchen Faucet, which turns the water on when you touch any part of the spout or handle with even the back of your hand. A simple but brilliant concept. Why has no one else thought of this?