Cheapest priced copy (Chronicles): $0.35 at Card Kingdom, near mint, their price list as of .
Giant Slug 
Creature — Slug · 1/1 · Common · Chronicles · #33
{5}: At the beginning of your next upkeep, choose a basic land type. This creature gains landwalk of the chosen type until the end of that turn. (It can't be blocked as long as defending player controls a land of that type.)
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Chronicles Foreign Black Border | 33 | Common | — | — |
| Chronicles | 33 | Common | $0.35 | — |
| Legends | 99 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 4 October 2004If the Slug changes controllers after the mana is spent, the player who activates this ability selects a landwalk during their next upkeep even if they don't control it at the time.
- 4 October 2004When the ability resolves, it creates another ability that triggers at the beginning of your next upkeep. When that ability resolves, you choose a basic land type.