By tools do you mean functions, or, like, add-on tools?
If functions, I think probably str_detect() for various text-processing workflows (important ones wherein I have to recognize character names in screenplays, say
), and str_trim() because ugh whitespace!
If "tools" probably Garrick Aden-Buie's RegExplain, which , granted, hasn't existed for all that long, but is amazingly helpful for (you guessed it) RegExps!