He's saving Boomer for a special occasion. Which is none of your business. She's not special enough, so there, hope that stings.

"Leave my grenade out of this." Sure it's her grenade but shut up he stole in fair and square.

"Shut up! I didn't say you won. I said you cheated." Which is totally different. Except no one cheats at losing. Not even backwards weird Autobots. "I don't need your stupid mercy. But you throw, and if I hit yours, you lose."

This is why you shouldn't try to cheat: you can't cheat a consummate cheater, Flashpoint.