Things like more Counterspells, Control (Opposition is a fav of mine, especially with tokens), commander disabling Darksteel Mutation
Homunculus Horde This alliteratively titled four-drop Blue rare is next
Beyond just being artifact creatures, many of these cards, like Crystalline Crawler, Hangarback Walker, and Threefold Thunderhulk, specifically synergize with counters
(Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.) Ravine Raider One black creature Lizard Rogue 1/1 Common Menace (This creature cant be blocked except by two or more creatures.) One generic, one black: Ravine Raider gets +1/+1 until end of turn
Lugia EX #17 Pokemon Japanese Classic: Venusaur Keep track of your collection value over time
Tiers are in no particular order