40-boxing

[Vicker]

Rather than having everyone holy nova at once, how about putting holy nova on round robin? I'm imagining three main keys:

One key has every priest cast PoM on himself.
One key casts holy nova on round robin.
One key casts hymn of hope on round robin.

Then you just spam that holy nova key as fast as you can. You can probably get about ten key presses per second. I think a continuously firing holy nova glob would be more interesting to see than all of them in sync. It would also use up your mana more slowly. You have forty hymns of hope at your disposal. Ten minute cooldown divided by forty priests means you get a hymn every fifteen seconds. You could do the same with divine hymn.

I also think it would be amusing to see them get hit with an aoe, causing every single PoM to jump at once.

Don't forget fear ward.

40x shadow fiends set to agressive.

Actually, you should do 37 priests and 3 death knights. Use the dks to round robin death grip to suck people into your holy supernova.

Edit:
Better yet, 40 dks, with glyphed rune tap and 40 ghouls set to aggressive. It'd be like a never ending army-of-the-dead-x5 with better ghouls. Plus you get your actual army of the dead, so you can crash the computer of everyone who's watching you. 40 dks + 40 ghoul pets + 320 army of the dead ghouls + 40 critter pets = 440 crash inducing entities running around.

[Owltoid]

I'd say all druids. Keep a rotation of typhoons where 10 cast them at once every 5 seconds. You can also get a starfall rotation going. Make some into resto and just wild growth spam to replenish mana and health of those all around, though not much will survive the typhoon and starfall barage.

Of course 120 treants would crash everyone's computer.