It's a tough choice but I think E3N is among my favorites of the E just because there's one mechanic that I forget about if I haven't run it lately, which is extremely good at killing me. And if I have run it lately, I like to call it out in party chat 5-15 sec in advance so everyone has time to react, at which point it will still claim victims.
And the music is amazing the entire time! Deaths and chairdancing, I can't ask for more. ♥