Combo

Combo is an ability where the stated effect occurs if the card is not the first one played from the hand during the turn. Cards with this ability are limited to the rogue class.

The term "combo" is also often used to refer to a sequence of cards or actions which are unleashed in quick succession, with or without Combo effects.

Strategy
If you use a deck with a lot of cards with Combo effects, cheap cards work really great since they can allow you to use a Combo effect easily. Backstab, for example, can be used to kill a weak minion, while you don't lose any mana playing it, which allows you to use a Combo effect for your whole mana pool. If you have too many Combo cards, you might have to waste a Combo effect to then be able to use other Combo effects.

The Coin can be used as a card to build up for a potential use of a card with a Combo effect. A classic tactic is to use The Coin on your first round, and then play Defias Ringleader. This will most likely give you a strong board advantage on your first turn since its Combo effect summons a Defias Bandit, a 2/1 minion. To improve this play, you can then use Shadowstep on your Defias Ringleader, and play it again, which gives you another Defias Bandit, therefore giving you two 2/1 minions and one 2/2 minion on your first turn. This play is one reason why playing second as the rogue is often considered an advantage. Similar plays utilizing combo effects can be enabled with cards that generate Coins or cheap spells, like Xaril, Poisoned Mind's Toxins or Razorpetal Lasher's Petals.

Headcrack is the only card that can be used to combo continuously. Because it returns to your hand and you draw a card each turn, you will always have at least two cards in hand.

Youthful Brewmaster has a great amount of synergy in Combo decks. It can return a Defias Ringleader or a 7 Agent before or after it has attacked, allowing you to re-summon it immediately for another Combo. Even returning a Defias Bandit can be useful to start a Combo on a further turn.

Combo-generating cards
This section lists cards which generate Combo cards.