At my parents' house, the shower bucket. At my house, the kitchen jug.
The water heater is at the other end of their house from the bathroom. My water heater is in the middle of the house, the kitchen is on the end. It takes awhile for hot water to reach their shower/my kitchen sink and dishwasher. So, in order to not just waste that clean if cold water by running it down the drain, we catch it and use it for something. I use it to water my vegetable garden.
Basically I fill my watering can from the cold water that comes out of the hot tap before I start my dishwasher.