Cheapest priced copy (Lorwyn): $0.35 at Card Kingdom, near mint, their price list as of .
Veteran of the Depths 
Creature — Merfolk Soldier · 2/2 · Uncommon · Lorwyn · #46
Whenever this creature becomes tapped, you may put a +1/+1 counter on it.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.35 to $0.49 at Card Kingdom
2 rulings from Wizards of the Coast
- 1 October 2007For the ability to trigger, the creature has to actually change from untapped to tapped. If an effect attempts to tap the creature, but it was already tapped at the time, this ability won’t trigger.
- 1 October 2007This is a triggered ability, not an activated ability. It doesn’t allow you to tap the creature whenever you want; rather, you need some other way of tapping it, such as by attacking with the creature.