Unidentified Cactus

[ArcanaCapra]

I bought this guy a year ago, and it's been growing very well in a huge variety of conditions (high humidity, low humidity, full shade, full sun, etc), but I dont know it's species. It has never flowered, too.

Can someone identify it?

 

[DragonsEye]

Some sort of Opuntia would be my guess.

 

[chch]

Same as the plant in the following thread
What is this thing?