@vaughnbros Restrict every card. One of everything!
I will say that highlander is a really fun format to play. I loved it when my friends and I played it before cube became popular (though to be honest, not a lot of difference between highlander and powered cube).
Highlander is less skill intensive I think (aside from deckbuilding) than Vintage, but such a deep card pool. Only issue I had was the lack of 4 wastelands makes LIbrary of Alexandria a little ridiculous.
If you're looking for a fun night, give it a try. Love the format!