The one I'm most grateful was invented is the sewing machine - I'm always amazed to think of some of the clothing that royalty wore at a time that all sewing was done by hand. For more "modern" times, it's the rotary cutter and cutting mat. Without that I might not even make quilts.
On an interesting note, the story is that the first person that came up with a sewing machine did not patent the idea because family convinced him it was a bad idea as it would put so many people doing hand sewing out of work.
The assumption was that consumers would not change their clothing buying habits, but when clothing became much less labor intensive and more affordable, people started buying more clothing ( a lot more clothing!) . So the sewing machine actually created jobs instead of taking them away.