Forest

Haliya, Ascendant Cadet

Whenever Haliya enters or attacks, put a +1/+1 counter on target creature you control.
Whenever one or more creatures you control with +1/+1 counters on them deal combat damage to a player, draw a card.

Herd Baloth

Whenever one or more +1/+1 counters are put on this creature, you may create a 4/4 green Beast creature token.

Plains

Meltstrider Eulogist

Whenever a creature you control with a +1/+1 counter on it dies, draw a card.

Have

Snakeskin Veil

Put a +1/+1 counter on target creature you control. It gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Arcbound Mouser

Lifelink
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Abzan Falconer

Outlast {W} ({W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has flying.

Duskshell Crawler

When this creature enters, put a +1/+1 counter on target creature.
Each creature you control with a +1/+1 counter on it has trample. (It can deal excess combat damage to the player or planeswalker it's attacking.)

Requisition Raid

Spree (Choose one or more additional costs.)
+ {1} — Destroy target artifact.
+ {1} — Destroy target enchantment.
+ {1} — Put a +1/+1 counter on each creature target player controls.

Botanical Brawler

Trample
This creature enters with two +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on another permanent you control, if it's the first time +1/+1 counters have been put on that permanent this turn, put a +1/+1 counter on this creature.

Wildwood Scourge

This creature enters with X +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on another non-Hydra creature you control, put a +1/+1 counter on this creature.

Longstalk Brawl

Gift a tapped Fish (You may promise an opponent a gift as you cast this spell. If you do, they create a tapped 1/1 blue Fish creature token before its other effects.)
Choose target creature you control and target creature you don't control. Put a +1/+1 counter on the creature you control if the gift was promised. Then those creatures fight each other.

Blossoming Sands

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {G} or {W}.

Selesnya Guildgate

This land enters tapped.
{T}: Add {G} or {W}.

Cankerbloom

{1}, Sacrifice this creature: Choose one —
• Destroy target artifact.
• Destroy target enchantment.
• Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Sunshower Druid

When this creature enters, put a +1/+1 counter on target creature and you gain 1 life.

Kutzil, Malamet Exemplar

Your opponents can't cast spells during your turn.
Whenever one or more creatures you control each with power greater than its base power deals combat damage to a player, draw a card.

Bretagard Stronghold

This land enters tapped.
{T}: Add {G}.
{G}{W}{W}, {T}, Sacrifice this land: Put a +1/+1 counter on each of up to two target creatures you control. They gain vigilance and lifelink until end of turn. Activate only as a sorcery.

Faithful Watchdog

Vigilance
This creature enters with three +1/+1 counters on it.

Gift of the Viper

Put a +1/+1 counter, a reach counter, and a deathtouch counter on target creature. Untap it.