Well, the one I'm running right now! I'm very pleased with tolkienekphrasisweek: I like the way I've combined the diversity and low stakes of a "fanweek-style" event with the exciting staggered reveals (and opportunity for better moderation) of Purimgifts. Coming up with the prompts is also always very fun, though definitely time-consuming.

And hey, I think there would be plenty of people who would do a McKinley-only event, if not exchange! Sometimes it seems like everyone on DW has read at least one of her books. And TEW "only" produced 60 works, but it was still really satisfying to see come to fruition.