Any Undead Boss in a Final Fantasy Game: Phantom Train? Gi Boss? Phoenix down and poof. Though, to be fair, any boss in FF history is a piece of cake if you've done enough side quests, seriously nearly I one shotted Omega in FFX with a three sisters combined overdrive at which point I decided that such power did not belong in the hands of mortals and never used the Three Sisters again.
Saint's Row 2: Vogel was a snooze to actually fight, the guy had a room full of armed men sure, but he still went down like a punk. Much easier than fighting Mero.
Chinese Commander in Operation Anchorage: Speech challenge him into suicide. Sure you can do the same thing with President Eden, and convince the Enclave Colonel to retreat, but the first time I did Operation Anchorage the Chinese commander was a bear to actually fight.
And to the guy using tanks to fight bosses in Prototype... smack yourself. Half the time tanks aren't available, and when they are you can't get into them because there are hunters ganking you every time you try. You're better off THROWING the tanks.