A GIFAR file is a polyglot file with a fancy name. It can be "opened" both as a valid GIF file and a valid JAR file thus leading to security issues under certain circumstances.
Definition of a GIFAR file :
Graphics Interchange Format Java Archives (GIFAR) is malware that allows an attacker to piggyback off the victim’s HTTP cookies. A GIFAR is a photo that can "borrow" a victim's online credentials, possibly taking over the web user's session.
GIFAR is a Graphics Interchange Format (GIF) image file combined with a JAR file. Altered GIF files can be uploaded to Web sites that allow image hosting, and run code that works inside that site.
Beside "GIFAR" are there any other known polyglot files?
I did try to answer myself and I couldn't find anything else. So I guess the answer might be no.