My favourite invention has got to be hot water on tap.
Being able to wash my hands with warm water, having a dishwasher and washing machine, the central heating, are things that give so much comfort to our modern lives! And I just love my hot shower in the morning. Especially as we got into a bit of a ritual with DB and DS. DB playing peek-a-boo while I shower and DS being an Octonaut, the sink his Ocean, standing on his little plastic step and splashing away with Kwazii and Peso :D