I'm a big fan of command-line tools and composable tools in general. I love being able to string outputs to inputs in a chain of manipulations to produce a result worth more than the effort involved in the automation. Unsurprisingly that leads me to favor unix-like environments with their focus on small utilities with narrow focus on function.
Tools I Use
By and large the tools I used have been selected for their efficiency and how available they are on the servers I support.
There are many other utilities I use on a less regular basis, but I'll address those in another post.
Before anyone gets too excited, yes, I do use powershell on windows. I really enjoy all of the options it brings. However, I spend a bigger chunk of my time on linux and OSX, hence the focus on tools for those systems.