There are a few permanents that offer more doubling up of counters, as well as ones that save counters from removed creatures, but even without these, Counter Blitz is very powerful right out of the box
In a strong second place is Sauron, the Lord of the Rings, which provides devastating value up front but costs a lot of mana and does surprisingly little after its ETB effect resolves
Cards like Boartusk Liege, Raph's Bravado, Hound Tamer / Untamed Pup, Unnatural Growth or Zopandrel, Hunger Dominus are also good ways to pay off having a board full of werewolves
Put that card into your hand and the rest on the bottom of your library in a random order. That means you get extra mana, mana-fixing, and card draw all on one handy card