I’ve been using this nice little program to generate the sound effects for Attack of the Meeplings

It’s very easy to use. Simply select a style, such as explosion, shoot, power-up etc.. and hit randomise a couple of times until you get the sound you like (or hit mutate if you only want a minor change.) You can also play around with all the parameters of the oscillator if you really want to understand the program in a little more depth.

The program is also open-source.