This is just a post for any to comment if they play any custom formats with their friends.
I play one. I'm not sure what it's called, but here goes:
1) You pick an uncommon creature to be your 'commander'.
2) You build a deck around them, using only common cards, and only card in that creature's color identity.
3) Play a game! We usually play with 4 people, but it works with any number, really (not something like '90', of course, but it works two-player).
4) Have fun! :D
And then there's always commander but with planeswalkers.