guitar

(for those too young to understand the reference: https://www.youtube.com/watch?v=PeMvMNpvB5M)

To more directly answer the question, not a big fan of flanging generally. I like phasers better which have a similar but more spacey effect.

yeah, flanger is super controversial 

i have never really liked it either, but I saw a video with someone using it on bass, and it sounded amazing

Eddie Van Halen made pretty tasteful use of it, e.g. in Unchained: https://www.youtube.com/watch?v=HUtqdiMqof0
Sounded pretty good for chunky 80s hard rock riffing (in moderation), but maybe not a lot else?  I really hate flangers on clean tones.

yeah, i agree 

a good phaser also sounds a lot better, adds movement without sounding too much like an effect