Cheapest priced copy (Oath of the Gatewatch): $0.35 at Card Kingdom, near mint, their price list as of .
Harvester Troll 
Creature — Troll · 2/3 · Uncommon · Oath of the Gatewatch · #133
When this creature enters, you may sacrifice a creature or land. If you do, put two +1/+1 counters on this creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Oath of the Gatewatch | 133 | Uncommon | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 22 January 2016Players can respond to the enters-the-battlefield ability (notably, while Harvester Troll is still 2/3), but once that ability starts resolving, it’s too late for any player to respond. You don’t choose which creature or land you’re sacrificing, if any, until the ability resolves.