In Hanna-Barbera's The New Adventures of Batman & Godzilla, the Caped Crusader teams up with Big G to protect Gotham City from its most notorious arch-villains. With Godzilla as backup, Batman soon discovers that the Joker, Penguin, Riddler, Mr. Freeze, and the rest are all, literally, toast.
But while you would think that being able to summon Godzilla to stomp on any costumed fiends (plus their henchman, their hideout, and the surrounding area) would put Batman, Robin, and Batgirl on Easy Street (a difficult neighborhood to find in a town like Gotham), the annoying sidekick double-team of Bat-Mite and Godzooky raises their stress levels through the roof until finally they are all diagnosed with PTSDS (Post-Traumatic Scrappy-Doo Syndrome) and confined to Arkham Asylum.
In Christopher Nolan's Batman vs. Godzilla remake, the Dark Knight is forced out of retirement one last time when the League of Shadows makes a final attempt to destroy Gotham City using a mind-controlled King of the Monsters to trample it underfoot.
Once Batman frees Godzilla from the League's influence, they team-up to fight Destoroyah, a giant monster created when the nuclear bomb that exploded in Gotham Harbor at the end of Dark Knight Rises mutated a colony of Precambrian crustaceans there, causing them to grow to 2 meters in size and eventually merge into one enormous, nearly unstoppable juggernaut. In the final battle, Batman and Godzilla must sacrifice their lives to defeat Destoroyah, and pass the mantle of protecting Gotham City down to Robin John Blake and Godzilla Jr. (although the franchise is rebooted again before either of them gets to star in their own movie).