The laziest thing I've done was during an internship:
We had to open big table files in a special software, click on some buttons and then save it. Each step took 1-5 minutes untilnwe could proceed with a click on the next button. So I wrote a click script, predefined the mouse positions and run it all day. This was able to run for 1 hour straight with no human action needed, so I started using the new sparetime for more interesting stuff: Gaming.