Windows: "Everything" (that's the name). A lightweight, fast and advanced (if you want it) file search engine. Linux: Most tools of course, as they are made with the Unix philosophy, but these days I'm most surprised by print drivers for Linux. Where in Windows the printer is always magically offline or slow, from Linux I can print and scan very reliably. Vim is also worth learning, it makes editing much more... rela…
If you've any latex pointers I'd appreciate it :) I used latex to write a paper for the first time last week, and while i thoroughly enjoyed it, i'm fairly confident there were lots of things I could've done better.
Use TeXstudio to write your documents. It is an IDE with autocompletion and contextual help and an integrated viewer. Made writing LaTeX so much easier, as it also has wizards to generate repeating boilerplate. I love Latex, especially mathematical notations are a breeze.