Double strike

Double strike is an evergreen keyword ability that allows a creature to deal combat damage twice per combat phase — once during the first combat damage step, along with any creatures that have first strike, and again during the second combat damage step along with creatures that have neither keyword.

It appears primarily in Red and in White, the two combat-trained colors already proficient with first strike. Even among cards that aren't red nor white, all but one (Planar Chaos card Jodah's Avenger) still require in some way to utilize double strike.

History
Double strike was designed by Wayne Alward, a player who submitted it as a mechanic for the first You Make the Card promotion. Double strike was rejected for the card, which would later become Forgotten Ancient because the mechanic didn't fit within Green's segment of the color wheel. Nonetheless, several R&D members were impressed with the design's elegance. Thus, double strike was adopted into Magic, upon which it became evergreen almost immediately.

Double strike premiered in Legions, with the cards Ridgetop Raptor and Rockshard Elemental. It remains an evergreen mechanic as of today.

Ikoria Commander introduced double strike counters.

Rulings

 * Double strike isn't first strike. Effects that make a creature lose first strike won't make it lose double strike.
 * Creatures with double strike and creatures with first strike deal combat damage in the first combat damage step.
 * All creatures that didn't assign combat damage in the first combat damage step assign combat damage in the second combat damage step. In addition, all creatures with double strike assign combat damage again in the second step.
 * If a creature has both double strike and trample, the combat damage it assigned during the first combat damage step will be considered when determining how much damage can trample through in the second combat damage step.

Cards that grant double strike

 * Planeswalkers
 * Ajani, Caller of the Pride (: target creature)
 * Ajani, Inspiring Leader (: creatures you control until end of turn, also flying)
 * Domri Rade (: emblem, your creatures)
 * Nahiri, The Lithomancer (: Equipment with equip, also gets +5/+5)
 * Samut, the Tested</c> (: target creature)
 * Sorceries (until end of turn)
 * Armed</c> (target creature, also +1/+1)
 * Assault Strobe</c> (target creature)
 * Cleaver Riot</c> (your creatures)
 * Sangrite Surge</c> (target creature, also +3/+3)
 * Victory</c>
 * Instants (until end of turn)
 * Boros Charm</c> (3rd mode, target creature)
 * Buccaneer's Bravado</c> (target Pirate, also +1/+1)
 * Double Cleave</c> (target creature)
 * Flying Crane Technique</c> (Creatures you control until end of turn, also flying)
 * Kaya's Onslaught</c> (target creature, also +1/+1)
 * Phalanx Formation</c> (any number of target creatures until end of turn, for extra  per target)
 * Psychotic Fury</c> (target multicoloured creature)
 * Raking Claws</c> (target creature)
 * Temur Battle Rage</c> (Ferocious — target creature also gets trample if you control a creature with power 4 or greater)
 * Savage Beating</c> (only during combat on your turn, your creatures (1st mode), also untap and have another combat if you pay its entwine cost of )
 * <c>Uncaged Fury</c> (target creature, also +1/+1)
 * Creatures
 * <c>Akim, the Soaring Wind</c> (: creature tokens you control until end of turn)
 * <c>Arashin Foremost</c> (entry or attacking, target Warrior you control until end of turn)
 * <c>Atarka, World Render</c> (whenever a Dragon you control attacks, it gains double strike until end of turn)
 * <c>Avatar of Slaughter</c> (all creatures, also attack each turn)
 * <c>Avenging Huntbonder</c> (double strike counter on target attacking creature)
 * <c>Bonescythe Sliver</c> (your Sliver creatures)
 * <c>Bruse Tarl, Boorish Herder</c> (entry or attacking, target creature you control until end of turn)
 * <c>Fury Sliver</c> (all Sliver creatures)
 * <c>Goring Ceratops</c> (when attacking, creatures you control until end of turn)
 * <c>Iizuka the Ruthless</c> (, sacrifice a Samurai: your Samurai creatures)
 * <c>Kinsbaile Cavalier</c> (your Knight creatures)
 * <c>Kor Blademaster</c> (your Equipped Warriors)
 * <c>Kwende, Pride of Femeref</c> (your creatures with first strike)
 * <c>Odric, Lunarch Marshal</c> (if one of your creatures has it, also several other abilities)
 * <c>Rafiq of the Many</c> (your creatures, when they attack alone)
 * <c>Raksha Golden Cub</c> (your Cat creatures if Raksha is equipped, also +2/+2)
 * <c>Resolute Blademaster</c> (creatures you control until end of turn, when ever an Ally enters)
 * <c>Shu Yun, the Silent Tempest</c> (: target creature until end of turn, when a noncreature spell is cast)
 * <c>Silverblade Paladin</c> (via Soulbond)
 * <c>Springjack Knight</c> (if you win a clash when it attacks)
 * <c>Sylvia Brightspear</c> (Dragons your team control)
 * <c>Terror of Mount Velus</c> (upon entry, all creatures you control until end of turn)
 * <c>Valiant Knight</c> (: Knights you control until end of turn)
 * <c>Veteran Cathar</c> (: Target Human you control until end of turn)
 * <c>Wrecking Ogre</c> (via Bloodrush)
 * Auras (enchanted creature)
 * <c>Armament of Nyx</c>  (enchantment creature only)
 * <c>Battle Mastery</c>
 * <c>Ghostblade Eidolon</c> (via bestow )
 * <c>Runes of the Deus</c> (red creature only, also +1/+1)
 * Enchantments (your creatures)
 * <c>Berserkers' Onslaught</c> (attacking creatures)
 * <c>Blood Mist</c> (one creature, beginning of your combat)
 * <c>Concerted Effort</c> (if one of your creatures has it, also several other abilities)
 * <c>Duelist's Heritage</c> (target attacking creature)
 * <c>Rage Reflection</c>
 * <c>True Conviction</c> (also lifelink)


 * Equipment (equipped creature)
 * <c>Embercleave</c> (equip, equips upon entry, also gets +1/+1 and trample)
 * <c>Fireshrieker</c> (equip )
 * <c>Grappling Hook</c> (equip, also forces blocking)
 * Land (undefined until end of turn)
 * <c>Sunhome, Fortress of the Legion</c> (,undefined)
 * Planes
 * <c>Bloodhill Bastion</c> (whenever a creature enters the battlefield, also gains haste)