Now that bunnies are confirmed it seemed logical to toss some suggestions around regarding their behavior and uses.

Behavior:

• Spawn in various biomes (maybe coloring will be based on biome)
• Jump 2 blocks high
• Can move through wooden fences
• Fast
• Run from players, villagers, wolves, and cats (ocelots)
• Wild and domesticated wolves and cats (ocelots) will chase them. Vary rare they will catch them though.
• Maybe burrow in the grown (similar to silverfish)
• Will destroy farms (eating young and mature plants and stems)
• Snow Golems are scared of them. Bunnies will attack them by jumping at their heads and chewing their heads off - Monty Python reference
• Can not be domesticated or breed (keep them wild)

Uses:

• Drops rabbit foot that can be used to make:
  • Luck potion (acts like a limited fortune enchantment)
  • Jump Potion
  • Speed Potion