"Shield" is not an ability that creatures have and shield counters are not keyword counters
For example, if Giant Growth had given one of them +3/+3 earlier in the turn, then Nanogene Conversion made it a copy of Bear Cub, it will be a 5/5 Bear Cub
Aurelia is a bit pricey at six mana, 3/4 with flying, vigilance and haste
1st Place: Manifold Mouse Ability versatility, nice, balanced cost, plus a chance to double up the card itself for the exact same cost when the opportunity presents itself
Only through the Helvault's destruction could Avacyn be freed to balance and protect the plane once againat least until the events of Shadows over Innistrad
Greel, Mind Raker Greel, Mind Raker strikes me as the worst horror commander because its discard ability targets a single player, and thats ineffective in EDH