Silent Hallcreeper

This creature can't be blocked.
Whenever this creature deals combat damage to a player, choose one that hasn't been chosen —
• Put two +1/+1 counters on this creature.
• Draw a card.
• This creature becomes a copy of another target creature you control.

Loch Mare

This creature enters with three -1/-1 counters on it.
{1}{U}, Remove a counter from this creature: Draw a card.
{2}{U}, Remove two counters from this creature: Tap target creature. Put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Ray Fillet, Wave Warrior

Flying
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Whenever a creature you control with a counter on it deals combat damage to a player, draw a card.

Wingspan Mentor

When this creature enters, put a flying counter on target non-Human creature you control.
{2}{U}, {T}: Put a +1/+1 counter on each creature you control with flying.

Endless One

This creature enters with X +1/+1 counters on it.

Iron Apprentice

This creature enters with a +1/+1 counter on it.
When this creature dies, if it had counters on it, put those counters on target creature you control.

Razzle-Dazzler

Whenever you cast your second spell each turn, put a +1/+1 counter on this creature. It can't be blocked this turn.

Storm Fleet Aerialist

Flying
Raid — This creature enters with a +1/+1 counter on it if you attacked this turn.

Faerie Vandal

Flash (You may cast this spell any time you could cast an instant.)
Flying
Whenever you draw your second card each turn, put a +1/+1 counter on this creature.

Flitterwing Nuisance

Flying
This creature enters with a -1/-1 counter on it.
{2}{U}, Remove a counter from this creature: Whenever a creature you control deals combat damage to a player or planeswalker this turn, draw a card.

Stonecoil Serpent

Reach, trample, protection from multicolored
This creature enters with X +1/+1 counters on it.