I have the classic things about backspace, black background, statusbar, hlsearch, autocomplete, etc.

Then I have a few shortcuts on <Function keys>, because these cannot override other bindings. The most important is <F9> linked to pastetoggle.

I also have some specific settings for my current main language (Python).

I try to avoid rebinding normal keys because it can kill you when you get used to your tweaks and have to use another instance, but one thing I do is imap <ins> <Nop>, because I hate being suddenly thrown in replace mode.

Plugins I have grep.vim linked to <F3> and I'm currently trying NERD_commenter.vim on <F6>