Aggro-control decks are decks that combine the ferocity of aggressive (aggro) decks with the control of, well, control decks. This combination of utility and speed make aggro-control decks, in my humble opinion, the most fun to build and to play.
Chances are quite good that the first deck you ever built was an aggro-control deck. Throwing all of your good cards of one or two colors into a deck tends to lead to this result. Unfortunately, aggro-control decks can be extremely difficult to fine-tune. In control decks the strategy is simple: keep a good handle on the game until you can, usually late in the game, finish your opponent off. Such decks include cards like Wrath of God, Counterspell, and Moment’s peace. Aggro decks are the exact opposite. These decks try to kill their opponents as quickly as possible. Ball Lightning, <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place w:st="on"><st1:City w:st="on">Savannah lions, and Troll Ascetic are all very aggressive cards. So why is building an aggro-control deck more difficult than building a deck of either of these two types? Because you have to do both at once.
Aggro-control decks must be able to win quickly against some opponents, and play the long game against others. The power of aggro-control is its versatility. When you sit down to build an aggro-control deck you need to be keenly aware of how many of each type of card (aggressive and control) you put in, since it dictates how well your deck can handle its multiple roles. As a general rule, you should be running 20-25 aggressive cards, 10-20 control cards, and 20-25 lands. Please keep in mind that there are exceptions to this.