The Eastern prickly pear (Opuntia humifusa) is an awesome hardy cactus native to much of eastern North America. In Michigan I have been growing it for close to a decade now, and from the small sapling I originally planted at our first place there it has multiplied into a number of large colonies scattered around my parents' current property, helped by the fact that the pads will root very easily and a number of pads often fall off from a plant during winter and spring. Of course, I eventually also brought some cuttings back with me as well, and now they are blooming for the first time.
Eastern prickly pear (Opuntia humifusa)
My success with other cold-hardy cacti has been limited so far, but I do have another species of Opuntia - though I am unsure which one - that has been growing in the Michigan garden for two years and when I was there a few weeks ago seemed to be setting flower buds for the first time.