Title pretty much says it all.

What I have tried:

Modulated comb filters on two channels panned hard l-r where the filter frequency of each side is different.

Two similar but not the same initial synth patches (previous to processing) panned hard l-r and bused for processing.

Creating another layer that's higher than main synth that has haas or delay based widening then take all the center out and layer it back in with the original sound after some processing.

obvious ones: detune/unison/chorus/haas/delay standalone fx etc...

Does anyone have any more techniques to share? I would love to have more tricks 

And also more importantly do you think mono is really that important? Maybe someone who has played on a large variety of stages could let us know if mono really matters for live performance? I know it's still going to be occasionally encountered but how often really?

edit: let me rephrase: How important is it really that your mastered tracks sum to mono nicely vs losing power in when summed to mono? Do most clubs and festival settings really sum to mono these days or is that just older people regurgitating how it used to be?