(Choose any number of permanents and/or players, then give each another counter of each kind already there.) Equip Whenever equipped creature deals combat damage to a player, put a +1/+1 counter on a creature you control, then proliferate
There is discussion on how to classify silver-bordered cards for casual play, and the Commander Format Panel has yet to address it specifically
It improves with cards like Voltaic Key that allow you to untap it cheaply, but we're still looking at a creature that dies to a wealth of removal spells
In Commander, this often ends up being used as a way to protect your Commander so you dont have to take a turn off recasting it
Then for each creature card you own in exile with a memory counter on it, create a tapped and attacking token that's a copy of it
Being able to use this at instant speed is a big deal, but it's also fairly easy to bring land cards back from the graveyard too, so Boseiju, Who Endures is likely to see a lot of play