Although shield counters are the most common, there are also +1/+1 counters, -1/-1 counters, and feather counters to name a few
Rush of Knowledge (Onslaught/Legions/Scourge) The common consensus in Onslaught/Legions/Scourge draft was that you wouldn't want to play a deck with more than two colors, since there weren't many cards which allowed you to "mana fix" - that is, fetch a third color of mana
As I mentioned earlier, there are a number of cards that can use the exiled cards as fodder for various effects in addition to just milling folks
Six mana is a lot, but Gilgamesh is worth it
Abilities that define a creature's power and toughness apply while that card is in your graveyard, but abilities that add or subtract from it don't
I like the wagon with the green cushions and the Oni-faced thing especially