Card

Lightning Greaves

Mana cost {2}

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.) Equip {0}

Part of 229 known combos, 3 of them two-card. 2 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Crackdown Construct, Cephalid Illusionist, Cephalid Aristocrat
B2 Core — Not in the same deck as its two-card combo partners: Crackdown Construct, Cephalid Illusionist, Cephalid Aristocrat
B3 Upgraded — Not in the same deck as its early two-card combo partners: Cephalid Illusionist, Cephalid Aristocrat
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Crackdown Construct, Cephalid Illusionist, Cephalid Aristocrat (early with Cephalid Illusionist, Cephalid Aristocrat)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

229 known combos, 3 of them two-card.

Monk Gyatso + Lightning Greaves
Produces: Infinite creature LTB, Infinite creature ETB, Infinite storm count
View on Commander Spellbook
Temur Sabertooth + Selvala, Heart of the Wilds + Lightning Greaves
Produces: Infinite creature LTB, Infinite creature ETB, Infinite colored mana
View on Commander Spellbook
Crackdown Construct + Lightning Greaves
Produces: Infinitely large creature until end of turn
View on Commander Spellbook

2020-08-07 · Wizards of the Coast
If a creature enters the battlefield under your control and gains haste, but then loses it before attacking, it won't be able to attack that turn. This means that you can't use one Lightning Greaves to allow two new creatures to attack in the same turn.
2020-08-07 · Wizards of the Coast
You can't simply unequip Equipment from a creature. If Lightning Greaves is attached to the only creature you control, you won't be able to attach other equipment to it (or target it with anything else) until you have another creature to which you can attach Lightning Greaves.

Rulings: Scryfall · Wizards of the Coast