Not sure if mathematics counts as software: Geometric / Clifford Algebra. It makes just about every aspect of handling geometry in computer graphics and robotics so much easier. It comes with a ton of upsides and only two downsides: You probably were not taught it yet (so you have to learn it) and if you do, others will have trouble following you unless they learn it too. I somehow feel like coming from a tribe where…
(I have a lot of skepticism about the geometric product as a useful object, but I think that multivectors are clearly fantastically useful everywhere. My exposure is mostly in physics where multivectors are basically necessary to make any sense of a bunch of concepts. But I don't work in robotics/graphics so maybe don't know how much good the geometric product does in practice?)