Ant
Tiny wins the battle.
Hard to Spot: Hostile mobs cannot spot you, so they will not attack you unless provoked.
Venomous Bite: You can give an entity poison by hitting them every 6 seconds with primary ability.
Speedy: You are fast.
Colony: You become stronger in groups, giving more strength but capping at 2.
Born in the Dark: You are given night vision since you live in the dark (shift to get the effect).
Climbing: You can climb walls, just like an arachnid.
Strong Feet: You do not take fall damage.
Tiny: You are very small.
Very Fragile: You only get 4 hearts.
Squash: If an entity lands on you it deals 1/2 heart of damage.
Dark Inhabitant: You can only sleep under the light level of 3.