My favourite invention was definitely the Internet! It has made so much knowledge available to the world at an instant and has improved communications making nearly anyone in the world, as long as you have access to it, available at any time. I guess some busy people might see that as a bad thing!
Electricity is a pretty major invention. It pretty much has led to all the developments of the last 150 years. If electricity were to disappear in the morning our industrialised society would grind to an instsnt halt. When the lights all go out during a storm in Ireland the candles ate fun for a few hours but the novelty soon wears off