Mana Flare

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Eladamri's Vineyard

At the beginning of each player's first main phase, that player adds {G}{G}.

Stadium Vendors

When Stadium Vendors enters, choose a player. That player adds two mana of any one color they choose.

Shizuko, Caller of Autumn

At the beginning of each player's upkeep, that player adds {G}{G}{G}. Until end of turn, they don't lose this mana as steps and phases end.

Valleymaker

{T}, Sacrifice a Mountain: Valleymaker deals 3 damage to target creature.
{T}, Sacrifice a Forest: Choose a player. That player adds {G}{G}{G}.

Belbe, Corrupted Observer

At the beginning of each postcombat main phase, the active player adds {C}{C} for each of your opponents who lost life this turn. (Damage causes loss of life.)

Spectral Searchlight

{T}: Choose a player. That player adds one mana of any color they choose.

Zhur-Taa Ancient

Magus of the Vineyard

Yurlok of Scorch Thrash

Vigilance
A player losing unspent mana causes that player to lose that much life.
{1}, {T}: Each player adds {B}{R}{G}.

Overabundance

Whenever a player taps a land for mana, that player adds one mana of any type that land produced, and Overabundance deals 1 damage to the player.

Blinkmoth Urn

At the beginning of each player's first main phase, if Blinkmoth Urn is untapped, that player adds {C} for each artifact they control.

Keeper of Progenitus

Whenever a player taps a Mountain, Forest, or Plains for mana, that player adds one mana of any type that land produced.

Heartbeat of Spring

Dictate of Karametra

Flash
Whenever a player taps a land for mana, that player adds one mana of any type that land produced.