For me it's the microsoft office suite. I used to make documents in LaTeX and continue in some cases for text heavy or math heavy final documents. Since using powerpoint however, I cannot image going back to either LaTeX or libre office for either presentation or quick intermediate reports. LaTeX is too cumbersome and libre office is just a pain to use (one part of me still hope that I am just using it wrong). Apart from that, gaming is also a reason for my personnal computer.