Here you can find extensive, high-quality sound libraries free for non-commercial and commercial use. Most of the listed libraries are royalty-free, however some sounds may require credits or licenses to use. Click the images to be taken directly to each sound library.
Sonniss and WeLoveIndies are both amazing sound libraries with high-quality sounds recorded by professionals. Their sound libraries hold hundreds and hundreds of unique sounds for any game development. While Sonniss has free downloadable sound effects, they also have bundles and deals you can buy for very cheap prices, especially if on sale. WeLoveIndies also has a huge range of sound effects also available for free for non-commercial use. They also hold royalty-free music to download as well. However, some sounds may require licensing in order to download.
This SFX generator is perfect for making chiptune-esque retro sounding game audio. It's quick and easy to generate and download and has many customizable features, including setting the waveform shape, frequency, flanger, and more.
These are general free sound libraries that are perfect for adding sound effects to films, animation, or any other project requiring high-quality sound effects. Fesliyan Studios and SoundGator are both royalty free. Zapsplat requires attribution for using their sounds, however if you'd like, you can pay for a license to relieve that requirement. Otherwise everything is free to use.