Ask HN: What tools have you written that had a great impact on productivity

The was a long discussion here[0] about the pros and cons of sharing tools/scripts to increase productivity but there weren't a lot of people describing what they've created. I thought it would also be a good discussion.

What have you created for your self or your team that helped boost productivity by an outsized amount?

[0] https://news.ycombinator.com/item?id=29486243