I play exclusively Commander and cEDH, so all of my picks come from there.
10.
Gemstone Caverns: My favorite land. It's a shame it's so damn expensive. Having a land enter the battlefield before the game starts means more mana on your first turn, so you effectively start the game on turn 2.
9.
Shaman of Forgotten Ways: The vast majority of the time, this guy is just mana ramp, and good mana ramp at that. But, every so often, you can activate his ability. If you do it at the right time (usually during the combat phase) you can take out everyone at once. If I can't have
Biorhythm, I will find another way.
8.
Mental Misstep: There are a lot of 0 mana counterspells in Commander, but this one holds something special for me. Just 2 life can answer so many problems. Any 1 mana spell in Commander is worth countering with
Mental Misstep.
7.
Paradox Engine: I can't talk about this one without getting emotional. It was great, and now it's gone.
6.
Containment Priest: The amount of game winning combos I have stopped with this card is unreal.
Flash Hulk,
Buried Alive, Vannifar,
Worldgorger Dragon, the list goes on. Plus she sticks around to prevent more combos.
5.
Sentinel Totem: Okay, real talk now; why don't more people use grave-hate in commander? This is a low-cost, instant-speed, budget card, that goes in any deck, and has an upside of Scry 1. Brilliant.
4.
Generator Servant: Mana ramp and a haste enabler. It should go in any red deck where your commander benefits from haste.
3.
Force of Vigor: Until recently,
Nature's Claim was undoubtedly the best one-shot artifact removal card in Commander.
Force of Vigor is the competition. Not having to pay mana, and being able to remove two things makes it great for eliminating annoying stax pieces, and for stopping combos.
2.
Bolas's Citadel: This card caught my attention as soon as it was spoiled. Being able to cast cards off the top is nice, but casting them by paying life instead of mana? Amazing. All you need after that is some way to get rid of the lands that periodically show up, and then you're set.
1.
Notion Thief: This dude. Wins games. First off, he turns your opponents' card draw into your card draw. Card advantage is very important in multiplayer, so giving yourself more draw, while denying your opponents draw is super relevant. Second, he has
flash. So just when your opponent thinks they are going to draw a card, you
flash him in, and you draw the card. Third, and this is the important bit, you can cast him in response to
Windfall, or
Reforge the Soul, or any other wheel effect. Your opponents discard their hand, and you draw all the cards they would have drawn. That almost guarantees a win in most matchups.