1/1 mtg card MTG's Lord of the Rings cards include an ultra-rare one-of-one One Ring Legal in Modern, Rules Text:

5 - Wan Shi Tong, Librarian - $54 Wan Shi Tong, Librarian can rack up counters, has Flash, Flying, and Vigilance, and gives you card draw, too

Being able to prevent damage to your creatures is good, and its even better when your commander has mana sinks built into them

Mind Bomb is another card that sees play occasionally, for its use in discarding unwanted creatures from hand, but I think its just worse than all of the cards above

Ultros, Obnoxious Octopus Ultros has too many teeth (though thats accurate to the games), and is a great card for limited with letting your midrange spells ice opposing creatures, while the 8 mana thing left to the realm of casual play in large

There are ways to stop extra turns from happening, of course

You can't change your mind and choose not to sacrifice anything