I'll have to get an image, but I made a card called "Fungal Cream". For 1 green mana you can use this Instant to remove all counters from a single Fungasuar. (I think that was the creature who could get +1/+1 counters simply by taking damage.)
EDIT
To do the mana cost, you type in a numeral for the colorless mana, then you type in the letters for the colored mana.
If you type in "3 g w r" You will have a card costing 3 colorless mana and one green, one white, one red.
Or "r r r" for just three red mana.