Sansevieria trifasciata (Mother-in-law's tongue, or Snake Plant). "When happy it produces strange green flowers" says my Indoor Gardening book.
The other night I was struck by a sweet fragrance in our living room. Curious, I went over by the window and inhaled the evening air, but it wasn't coming from outside. Then I noticed the intense fragrance coming from the snake plant right next to the window! It releases it's perfume only at night- like a nocturnal secret.
I've had this plant for some 8 years, repotted maybe once (really due for another repotting) and never have I seen the strange blooms it is capable of producing until now. I guess it is a very happy plant! And that makes me happy :)