Sixtyforce is a shareware Nintendo 64 emulator for Mac OS X. It natively supports both x86 and PowerPC-based machines.
Sixtyforce doesn't support as wide a range of games as Mupen64Plus (the only other active Nintendo 64 emulator that supports Mac operating systems, aside from the obsolete TrueReality emulator), but still supports PPC: most games that work run at playable speeds on late-generation G4 and all G5 processors.
Like Mupen64, Sixtyforce uses a plugin-based system to allow for a wider range of game support.
Sixtyforce is offered both as a free or paid version. The free version lacks save states and displays the "SixtyForce" logo on the bottom of the screen during play. In the paid version, which costs $14.99, saving states are allowed and the logo is removed.
Since version 0.9.2, the source code for Sixtyforce was not released. Thus, Sixtyforce is now proprietary software.