I believe I mentioned this before, but
Minor Misstep has become a blue staple in both my normal playgroup and the cEDH group I play with at my LGS. Yes, it costs 1 but it can counter sol rings/mana vaults or cheap draw, but also 0 cost rocks.
Also,
Countersquall is a decent C-tier non-creature counter that has saved me a couple of times when running my dimir/multicolored decks. For only 2 mana it's as good as a
negate, plus a little damage to an opponent as an added bonus.