Hello Vik,
I was thinking along the lines of the many Macro based viruses that are sent in Mac Office file formats. Also, scanning of Mac based compressed files, .sit, .hqx, .tar (Mac OS X), .gzip, etc.
Example of Macro Viruses:
MelissaW
More Popular Mac Viruses
AplS/Simpsons-A
SevenDust
CODE 0911
MBDF
-Ben