Not long time ago, i had discovered amazing source of quality 8-bit sounds, if you understand what i mean by saying word "quality".
SFXR is a true classic frequency modulation synthesizer. Besides essential stuff like pickup/coin/laser/boom/powerup/blip/hit/jump sounds, program has an ability to generate completely random audio from scratch, with fully customizable tweaking of newly created sounds.
For people who don't want to get into nerd stuff there is an easy button, called MUTATE. Press it multiple times for achieving needed articulation. Export to wave feature makes me love this application even more. Software will be helpful for sound designers and music composers, who are allured by 8-bit bleep'n'bloops. Some screenshots for detail.
Classic bleep'n'bloop presets