We used to play mono-rby with Psychic and Normal banned. It leaves you basically choosing between Poison, Water and Electric.
Electric loses to heavily anti-electric Poison, Poison can kinda go either way, but it will probably lose to Starmie anyway, and trying to beat Water with Poison hurts your ability to beat Electric, which wasnt exactly a free win at the best of times. Ground is an even more anti-electric/water weak poison, and Rock is a much worse Ground. Grass isnt really good enough, though maybe with wrap it might have a bit more to it. Ice is Water except that it loses to Water, plus it only has 5 pokemon. Dragon and Ghost dont require a lot of explanation. Flying loses to electric and doesnt really have an advantage against anything else. Fire and Bug are fire and bug. Fighting doesnt really beat anything seeing as how Normal is banned.
Maybe banning Electric could level things a bit. Or UU mono might level the playing field a bit. Certainly would make Psychic bad.
In terms of OU, Psychic and Normal can do this easily.