With more and more uncommon legendary creatures printed with every set, there's a whole tranche of powerful commanders who don't command premium prices
There are some powerful reanimation style commanders that have since come out but Karador still holds his own because of his ability to subtract his rather high casting cost of 8 for 1 mana for each creature in the graveyard
An Edgar deck aims to flood the board with a swarm of low-cost Vampires, each one bringing a friend along for the ride
Scions & Spellcraft doesn't have quite as many of those nasty surprises as we might hope for, but card advantage is card advantage, and in a precon, that's nothing to sneeze at
Its controller draws a card
There are cards that trigger other special abilities whenever you sacrifice a land (like making extra creatures to fill up your board) and cards with various Landfall abilities that do cool things whenever you play a land (like getting an extra combat step)