cfxr is a Mac port of 8-bit and 16-bit sound effect creator sfxr. It provides a high degree of control over various sonic qualities for four types of wave: square, sawtooth, sine, and noise. There are also eight game-oriented presets which create a random sound within specific parameters. Sounds can be exported in WAV format.
There are 22 different features available for user adjustment, each of which can be tweaked very finely. Whether you want a retro explosion sound with a slow attack or a retro jump sound with deep vibrato, the possibilities within the low-bit realm seem endless. There are also various playback options: the sound can be played when it's changed, on loop, and/or on demand with a button press. Playback volume and sample volume are controlled independently, and there are two choices for sample rate: 44.1 kHz and 22.05 kHz. Topping off the features is an automatically generated sortable catalog of sounds with a rating system, should you like all your experiments for a particular project in one place.
I experienced choppy in-app playback under Mountain Lion, but the exported sound clip plays back just fine.
