Whats a card ability you really want to see?

Ive seen a lot of ideas floating around but i would love to see some interesting ideas from you guys.

One idea I genuinely want to see more than anything is a simple one:

Shuffle your hand into the deck and draw 3 cards.

Its a simple idea but a staple of card games. Basically the mulligan play, it has risk reward.

Another cool idea might be:

Activate: force one of your opponents cards to switch sides with this one.

This would have to be a low stat line card to make it viable but it again has risk reward.