I mostly write Python code. After scouring the internet and watching lots of VIM videos, I've gotten my .vimrc to be just right for me.
My biggest influence has been amix's ultimate vimrc repo, and Leeren's amazing youtube talk.
If there was one line of code I'm most proud of, it would be <leader>p.
Whatever text you yanked (both line and characterwise), is pasted on the next line and auto-indented. Really useful if you're working with any indentation enforced languages.
Some of the :term code using <leader>t isn't bad either :)