Cheapest priced copy (Ravnica Allegiance Promos): $0.49 at Card Kingdom, near mint, their price list as of .
Gruul Spellbreaker 
Creature — Ogre Warrior · 3/3 · Rare · Ravnica Allegiance Promos · #179p
Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Trample
During your turn, you and this creature have hexproof.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica Allegiance Promos | 179p | Rare | $0.49 | $0.99 |
| Ravnica Allegiance Promos | 179s | Rare | — | $1.29 |
| Ravnica Allegiance | 179 | Rare | $0.49 | $1.49 |
3 rulings from Wizards of the Coast
- 25 January 2019Riot is a replacement effect. Players can’t respond to your choice of +1/+1 counter or haste, and they can’t take actions while the creature is on the battlefield without one or the other.
- 25 January 2019If you choose for the creature to gain haste, it gains haste indefinitely. It won’t lose it as the turn ends or as another player gains control of it.
- 25 January 2019If a creature entering the battlefield has riot but can’t have a +1/+1 counter put onto it, it gains haste.