I'm running Mountain Lion and anytime I try to launch Spelunky it says that it can't because it is damaged and offers to move the file to the trash.
What's going on? I get this with the 1.3 posted here, as well as the older 1.0 port.
Edit: It appeared to be the security setting preventing "unidentified" developers and non-App store apps from being run. Hadn't encountered this before but it seems to work anyway.
For anyone else having this problem, the following guide explains how to change the necessary setting in Mountain Lion. I hope that helps.