Who needs it: Every deck
"Sad Robot" is never a bad choice for an EDH deck and should be an automatic inclusion in every deck. He's colourless mana-ramp as well as colourless card-draw. I've never been sad to draw this card. In my Maga, Traitor to Mortals deck, I've reanimated other people's Sad Robots just to get extra land out so I have less chance of drawing them on my turn. He also makes a great attack deterrent since no one wants to give you free card draw.
Spine of Ish Sah
Who needs it: Every mono-coloured deck
Now you may be saying "it's 7 mana to destroy one thing; it's too expensive", but consider the fact that not every colour can deal with every problem. Let's go in WUBRG order to explain.
- White cannot deal with lands. Now, this may not seem like a huge issue, but when you're staring down a black deck with a Cabal Coffers, you'll be saying something completely different.
- Blue can't really deal with anything once it's hit the field. Sure, it can Boomerang anything and then Rewind it, but by then you're spending 6 mana over 2 cards to do that, putting you at a huge card disadvantage.
- Black can't deal with lands, enchantments, or artifacts. Older cards like Sinkhole and Phyrexian Tribute do exist, but they are either too expensive money-wise to get a hold of or are too bad to run.
- Red can't deal with non-artifacts or non-lands. Chaos Warp exists, but that's a whole one card in red's arsenal to deal with creatures, enchantments, and planeswalkers. Red does have direct damage spells, but many of them are too weak to warrant running in EDH (remember, you're opponent has 40 life, so those spells are at half-power essentially).
- Green can't deal with creatures in general. Cards like Wing Snare exist, but they're situational at best. Beast Within is an omni-solution, but it's only one card and you may need it for another problem.
This should also be in a lot of dual-colour EDHs as well, especially if the two colours don't cover each other's weaknesses (blue-black, for example still can't deal with enchantments, lands, or artifacts whereas white-red can deal with anything).
Who needs it: Every deck that runs white
Mono-white land search. Need I say more? It allows you to keep up with your opponents' ramp. Also, it lets you look for non-basics. Again, need I say more?
Who needs it: Every deck that runs blue
Free counterspell. FREE counterspell. Free COUNTERSPELL. 'Nuff said.
Who needs it: Every deck that runs black
Now this may require a little explanation. The reason I love this card is because no one expects it to do as much as it does. First, it steals then exiles a creature from someone else's graveyard but it also acts as anti-boardwipe tech. This is a rough transcript of what happened in a game between my Maga deck, a Kresh the Bloodbraided deck, and a Kaalia of the Vast deck:
Kresh: I put Darksteel Plate on Kresh.
Me: I take it. It's bigger than Kresh since every graveyard now has around 30 cards in it.
Kresh: Damn it. Fine, I'll just wait for you to exile it at the end of the turn and kill you next turn!
Me: At the end of my turn you mean?
Kresh: Damn it! Fine, I'll wait until the end of your turn! I end my turn.
(Kaalia is sad for a turn)
(My turn comes around)
Kresh: ...I scoop. This game is dumb...
Who needs it: Every deck that runs red
This is red's omni-solution. 'Nuff said.
Who Needs It: Every deck that runs green
This is green's omni-solution. 'Nuff said.
That's the first part of my possibly-many-parted EDH post series. Hope you found it helpful!
P.S. My next post has been in the making for 2 weeks now, so sorry for the wait.