...played all those cards listed, and I must say...from all of them, Mother of Runes and Mogg Fanatic really stand out above most.
They're just simple, 1/1s for one mana...yet they each do more than they can handle.
Mother of Runes can't be beat. She does it all. I even questioned her existence when I first saw the spoiler for Urza's Legacy...at least, I thought, she would've been a rare. Even at rare, she would've been played.
Mogg Fanatic is THE best Red, 1-costed creature, simply because you NEVER have to worry about it dying without at least dealing 1 damage. It kills most of the other good 1-costed critters too.