Since I'm working in git repos the majority of the time, I type these hundreds of times per day:
alias s="git status"
alias d="git diff"
I prefer looking at this stuff in a terminal rather than an IDE. Reducing them to a single character just feels so good. Note: not a git alias like "git s", literally just the single character "s" in Bash itself.And coming in third:
alias ..="cd .."