Hemerocallis 'May May', hybridized by Hayward way back in 1976. While not the flashiest flower in the garden, it's a tremendously reliable rebloomer.
Hemerocallis 'Height of Fashion', hybridized by Mike Huben. Although its ancestors are rebloomers, it does not exhibit rebloom traits in the MA garden in which it was hybridized. When crossed with other rebloomers, the trait reappers in subsequent generations.