Very short beats which can be played as-is, arranged/timestretched into more conventional beats, or loaded into a sampler, thereby playing a beat made of beats.
Burst of air next to a mic. It was originally intended for a bullet hitting a ballistic vest, but it obviously can work for some kind of a pressure releasing sound too.
Singing canary. This sound is public domain. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.