I think the Super Iced Grapefruit and the Purple Envy are contenders for that. They've been really stable genetics and all have looked the same. I'd add Crown Royale to that list judging by my girlfriends grow. I'd love to do a monocrop and just keep cloning and doing it over and over in one of my tents but I've been so spoiled by getting to try all these different strains all the time. I used to be more on the search for the right strain but now I'm realizing I am loving just trying all these different breeds. It's going to be very hard to do a monocrop for me. I just pretty much smoke my stuff and don't want to go to a dispensary at all. I have one friend who grows who I can exchange with but growing all one strain would be a lot of weeks of the same smoke over and over.
I bet you see me do a one plant in a 4'x4' setup with a scrog before you see me do a monocrop. I like the challenge that the one plant in a tent brings even though I still don't like the concept of having a full yield of just one strain.