Mega Pokemon from a competitive standpoint

Mega evolution is an epic feature, we all know. I was wondering what Mega Pokemon to use in an Ubers Competitive team, but I kinda want something a little different to the generic "Get a Salamence" or "get a Mewtwo"

I test mega teams on Showdown, but I am still not the best at team building and I wanted some advice

Can anyone give me some on the lesser used Mega Pokemon with Ubers strategies?
Thanks

I did actually try that, the hex gengar, but when I ask for strats on less common megas, I mean like UU tier and even RUBL and NU tier Megas (although I think any mega can make it at least in UU)

I have discovered that M Slowbro has an ubers strat and that Steelix M can be used in OU effectively.

I was wondering if anyone has developed a viable strat for a mega like abomasnow in OU or something like M houndoom in OU?

That sort of thing

Isn't mega gengar primarily used as a destiny bond trapper? While it can hit fairies, psychics, and ghost types hard it is still vulnerable and it's defenses are trash. So you're better off running more shenanigans with m gengar than a special sweeping set