Walking BallistaI don't get this card. Even pros in standard run it, yet every time I've played it it's been completely and utterly underwhelming. I get that standard decks have to interact with the combo, but still. People are putting this main deck, not in the sideboard, which sounds absurd to me.
1) This card is a 2-mana 1/1, 4-mana 2/2, 6-mana 3/3, etc. At each of these points it is way overcosted.
2) This card virtually never trades at mana parity. For example a 4-mana Ballista
can kill Thalia, Heretic Cathar, but you'd also have spent 4-mana to kill a 3-mana creature.
3) In the ideal scenario, you will kill something and still remain around (to chump, charge, etc). But this never happens. To kill the same Thalia without dying you need to invest six mana into it, which is absolutely tremendous. To kill Gideon, you need 10 mana. It's simply way too mana intensive.
4) Finally it does act as a mana sink, but it's an excessively expensive mana sink. For four mana I'd expect something like "draw a card" or "opponent discards a card" (there is actually such a card,
Prophet of Distortion). There are also other excellent mana sinks such as Oviya and Tireless Tracker.
The only time I can see it as being good is if something else puts the counters on it. Winding Constrictor is the obvious example. But aside from that deck I don't see this as an option at all. Yes it can flip Archangel Avacyn at will, but Avacyn's a mythic. Every time I put Walking Ballista in a deck, even if I'm running massive ramp, I have been disappointed. Why do people use this card at all?