I won't say that these plays are uncommon but you should read them and they are not usually the popular ones put on by community theaters or revived very often:
"The House of Blue Leaves" - John Guare (I would suggest that you look for other Guare plays as well)
"Balm in Gilead" by Landford Wilson (again also look at some of his other plays like "The Rimers of Eldritch")
A lot by Sam Shepard. One of my favorites is "Buried Child" and there is also "Curse of The Starving Class" and many more.
There are so many plays out there and if you can be more specific about what you are looking for then I'm sure you would get some help.
"Smart! And into all those exotic mystiques -- The Kama Sutra and Chinese techniques. I hear she knows more than seventy-five. Call me tomorrow if you're still alive!"