In the English translation of Astérixin Spain, Asterix and Obelix rescue a small Hispanic boy from his Roman captors. They are quickly dealt with and Obelix exclaims in disgust, "Molesting a child! I've a good mind to straighten them out some more!" Let's think (and hope) that he meant the old meaning...
The Romans from the Asterix books frequently have 'orgies', in the old sense of 'rowdy indulgent party' (one hopes).
In the French version of Asterix and the Goths, Getafix asks for "un druide débile". "Débile" used to mean weak and feeble, but nowadays is used almost exclusively to mean "dumbass" or even "retard".
The English translation of The Red Sea Sharks: Tintin, Haddock and a shot-down (male) Estonian pilot are adrift on a raft in the middle of the Red Sea. They eventually are sighted by some passengers in a cruise ship, after which a woman immediately shouts to the ship's millionaire owner, "Look! Shipwrecks! How madly gay!" The series in general also used "queer" to mean "strange" quite often.
Also, the references to "coke". At the time it was widely used to refer to as a derivative of coal, but nowadays "coke" usually refers to either Coca-Cola or cocaine. The latter interpretation makes Haddock's shocked reaction to Tintin's question if their ship is carrying any coke look particularly hilarious.
In The Broken Ear, a South American artifact is repeatedly called a "fetish", with the word's older meaning of "idol" rather than the modern meaning of a sexual fixation.
In the 1950s, "boner" was just a slang term for mistake (e.g., the Merkle Boner in baseball). So it didn't raise anyone's eyebrows when a Batman story had the Joker start a crime wave based on "boners." The result was dialogue like "Laugh at my boner, will they? I'll show them! I'll show them how many boners the Joker can make!", "This emphasis on boners has given me an idea for a new adventure in crime!" and "I'm worried about the boner he's readying for you!" The Joker takes inspiration from a picture that "shows a big boner of modern vintage!" And to top it all off, the cover portrays the Joker as a giant totem pole. Not surprisingly, this story became an Internet meme. It was also drawn by Dick Sprang.
This example also shows up in a contemporary Spider-Man comic—after Spider-Man embarrasses himself by breaking up an apparently villainous act by the Human Torch that turns out to be You Just Ruined the Shot, a bystander comments "I guess anyone can pull a boner".
And because it seems there's not a single word on this page that hasn't appeared in at least one vintage Batman comic, here is: Batman's leather thong .
In one comic, Batman is carrying Robin out of a hospital, saying "I've got news for you, Robin! Wait till you hear what Gordon has up his sleeve" and Robin is thinking "Batman's doing his best to sound gay. But I can tell his heart isn't in it!"
In DC Comics, Speedy (Green Arrow's Ward) once points out "Y'see, my straight friends and I no longer had anything in common." He means "Y'see, my non-drug-taking friends and I no longer had anything in common." The sentence can be converted to modern vernacular, though, if you tack "-edge" onto the end of "straight"; maybe future printings will take advantage of this. His name didn't escape many people, either.
Similarly, Jim Wilson in 1972's Hulk #157, thinking about Maj. Glenn Talbot: "The Major isn't a bad guy... just so awfully straight, it makes your backbone ache!". For extra fun, Wilson would come out about 20 years later, in the Peter David run.
In 1942, Gardner Fox and Howard Purcell created a swashbuckling hero who battled evil from beyond the grave. His name? The Gay Ghost. He reappeared in Grant Morrison's Animal Man as a resident of Comic Book Limbo, where he said he didn't want to be brought back because of the redefining of the word "gay." He was later brought back anyway, but as The GRIM Ghost. In his inaugural story, the word "queer" comes up several times, and his ability to possess the bodies of the living is described as "the power to enter men's bodies". (Via Cracked's The 5 Most Absurd Superhero Names of All-Time.)
With the sheer number of times they remind you this is about Gay City before Supes even gets there, this appears to be a case of Viewers Are Goldfish transformed into Overly Long Gag.
An early issue of The Invincible Iron Man includes the gem: "Little did she realize that Tony Stark had to leave the gay party for a most unusual date—with an electric cord!"
In Life in Hell gay characters Akbar and Jeff are confronted by an angry hulk who asks them "How come you guys took a perfectly good word - 'gay' - and ruined it for the rest of us?" (This coming from a guy who has clearly never been merry and carefree in his life). Their response is "We call ourselves gay because we are gay." as they push him over, in a merry, carefree way.
There's a line in Catman's Who's Who entry about "the cat fetish he acquired in Africa". In proper context, it's easy to tell that the subject is a totem carving of a cat that he picked up while he was in Africa. Outside of that context or to the casual reader is another story. (The original meaning comes from Portuguese, meaning that in Portugal, Brazil or Angola the reference wouldn't be quite so naughty.)
Captain Marvel himself debuted (and frequently starred) in Fawcett Comics' Whiz Comics, and Billy Batson was a contributor to radio station WHIZ. Fun fact: both of these were named for an older Fawcett publication with an unfortunate name, Captain Billy's Whiz Bang.
There are old Beano comic strips called Little Dead-Eye Dick and Cocky Dick (Cock and Dick both being contemporary British slang for penis) . Also in an old Bash Street Kids strip Smiffy points at a stuffed lion which Danny has stuffed his head into and says "What a big pussy!" (Pussy is slang for vagina, but can be used to describe a coward. It was also a common British term for cat, which is the more likely meaning here...).
Issue #16 of Fantastic Four has Johnny exclaim that he finds fixing his car the most fun activity "...next to flaming on."
Similar to the "bisexual" example on the main page for this trope, a mid-1970s X-Men comic describes a space crew with both male and female members as being "inter-sexual", by analogy with "interracial".
Comic letterers often used shortened versions of words in order to save space in word balloons, such as using "thru" instead of "through". A once-popular example of this was "howcum" instead of "how come". This isn't used anymore for obvious reasons.
The language of the Greyfriars series is parodied shamelessly in a story from the old Brain Damage comic where girls are allowed into the world of Boys' School stories and are being very assertive. Poor old Cherry just has time to ejaculate "Hello, hello, hello," cheerily when he's shot dead by a girl with a cry of "He'll not ejaculate cheerily again, I'll wager!"
Deadpool: My name is Wilson. Wade Wilson. I'm a dick. A private dick. A DETECTIVE! Never mind...
Lampshaded in this example. Though it made it onto the "Seduction of the Innocent Page" (a collection of examples of this trope), the last panel winks at the audience.
Deliberately inverted in an issue of Midnighter's solo series, in a time travel arc. In the 40th century, Everyone Is Bi, so when the Midnighter says something about being gay, a character from that future says, "I don't understand. What does being happy have to do with sex?"
An issue of Superman, a retired super-villain announces that he was once known as The Molester. The reactions of his friends force him to point out that back in the day, "molest" meant "to bother". (Joker and Prankster were already taken, you see.)