speculator (n.)

• adventurer
• bettor
• boneshaker
• cardsharp
• cardsharper
• casuist
• cosmologist
• doctrinaire
• gambler
• gunslinger
• operator
• philosopher
• philosophizer
• player
• plunger
• punter
• scalper
• sharp
• sharper
• sharpie
• sophist
• sport
• sportsman
• stag
• theoretician
• theorist
• theorizer
• thinker
• tipster
• tout
• venturer
• wagerer