I have been a fan for a very long time of Marvel's What if series and DC's Elseworlds. Marvel is supposed to be starting a new What If series this Fall. DC will still put out Elseworld stories, but without the Elseworlds label. I think the Another Nail series is like that.
Some of my favorite Elseworld strories: Kingdom Come, Golden Age, Darkest of night (Bruce Wayne becomes the GL) Speeding Bullets (Kal-el is adopted by Thomas Wayne, becomes Batman after their deaths), some of the Elseworld annuals (World without Superheroes, The Flash annual from that year, Superman annuals that year with the Earth invaded and the heroes having to go underground, JLA defeated by Felix Faust).
Torqumada