This free plugin from Softube is a superb download you can use on your mixes.
It ads a subtle to heavy distorted saturation on the output, to ad that little bit of grit or heavy gritty sound like an overdrive.
Used to give your bass sounds some fatness or by adding some harmonic frequencies to any vocal part.
It also does some wonders on drums and can even be used on the master buss.
Play around with this “Oneknob”