Here are some synonyms for "corny":
* Cheesy
* Clichéd
* Overdone
* Uninspired
* Lame
* Tacky
* Gauche
For example, you might say:
* "That joke was so corny!"
* "The movie's plot was incredibly corny."
* "He tried to pick her up with a corny pickup line."
It's important to note that "corny" can be subjective, and what one person finds corny another might find charming or nostalgic.