Looney Tunes, anyone? Chances are, for example, if Bugs Bunny is in it, the toon's title will often make a pun with the word "hare", "rabbit" or "bunny". Famous titles include Hare Trigger, Rabbit Fire or Ali Baba Bunny.
Same for Road Runner shorts, which usually have titles that're puns involving either the Road Runner's superspeed (or uttering of "Beep! Beep!") or Wile E. Coyote's tendency to get maimed (Fast and Furry-ous, Zoom At the Top, Wild About Hurry, To Beep or Not To Beep, Gee Whiz-z-z-z-z-z-z, Boulder Wham!, Scrambled Aches).
The king of Western animation pun-titles is likely the Jay Ward shows, particularly Rocky and Bullwinkle. Each R&B story ended in a cliffhanger ending, with the narrator giving two possible episode titles, both of them usually puns. Example (when Rocky's strapped to a runaway missile): "'The Squirrel Next Door', or 'High, Neighbor'!"
Especially in later seasons, most of The Simpsons episode titles are puns such as "Mobile Homer", "Moaning Lisa", or "The Bart of War."
The Mona Lisa, in fact, is one of the most frequent target of parodied episode titles; there have been at least three episodes whose titles use that pun, while the others are a more diverse - the only other recurring theme is "<member of the Simpson family> vs. <plot point>".
My Little Pony: Friendship Is Magic has a few, like "The Stare Master" (a pun on the StairMaster exercise device), "Griffon The Brush-Off" ("Given the Brush-off"), "Owl's Well That Ends Well" (All's well that ends well) and "Lesson Zero" (less than zero).
There's also "Magical Mystery Cure" (Magical Mystery Tour), "The Ticket Master" (Ticketmaster), "Boast Busters" (Ghostbusters), "Look Before You Sleep" ("Look before you leap"), "Feeling Pinkie Keen" ("Feeling peachy keen"), "A Friend in Deed" ("A friend indeed"), "Castle Mane-ia" (Castlevania), "Filli Vanilli" (Milli Vanilli), and "Secret of My Excess" (The Secret of My Success).
The 1973/74 Super Friends episode "The Shamon U". The title device was a U-shaped giant gold-attracting magnet owned by the villain. Its title was a pun based on the phrase "Shame on you".
Pound Puppies (2010) tends to use these fairly often. Examples include "Prince and the Pupper", "Mutternal Instincts", and, perhaps slightly less groan-worthy, the Halloween Episode "Nightmare on Pound Street".
Aside from the obvious Punny Name of Gravity Falls, there's also the episodes "Tourist Trapped", "Headhunters", "The Hand That Rocks The Mabel", "Double Dipper", "Irrational Treasure", "Little Dipper", "Carpet Diem", and "The Land Before Swine". And that's just the first season...