Advance Wars, Which didn't used to be as obscure but it's sister series Fire Emblem kinda knocked it out of the water when Awakening came out.
Command & Conquer: Not Extremely obscure, but like AW above, it has become more obscure in recent years. Great RTS series, but EA killed it with the C&C 4: Tiberian Twilight.
Total Annihilation; Another good RTS fromthe era when most RTS's were born. Very Unique build system, and is the spiritual patriarch to games like Supreme Commander.