Macintosh

This article is for games released on Mac operating systems BEFORE OS X.

Emulators
Earlier versions of Mac OS X had OSX Classic mode you could use to run pre-OS X applications, including games, but newer ones might not have it. If you're on another operating system, there are emulators which can act like a Mac OS of your choice. However, with most of them you need to have a ROM image of the required computer, and either a CD or disc image of the OS you want it to use.

Mini vMac is a virtual Macintosh Plus, and can run OSs from 1.1 to 7.5.5. It's for the games with black-and-white graphics with no shades of gray.

Basilisk II a virtual 68xxx Macintosh, that runs OSs from 7.x to 8.1. You can try it with the earlier Mac games that were in color.

SoftMac is a windows-only emulator of 68xxx based Macintoshes.

Executor is a Windows/Linux emulator for 68xxx Macintoshes that used to be for-pay, but the owners released a special reg key to the public so anyone can use it now. Does not require the ROMs from the original Macintosh.

SheepShaver is a Windows/Linux/OSX emulator that works as a virtual PowerPC, and it runs OSs from 7.5.2 to 9.0.4. This might be the best replacement for Classic mode if you're on an OS X installation that doesn't have it, but it requires a ROM image and a copy of Mac OS.