there is tons of oscillators out there and they all can do the job. usually one would choose function generator as a flexible signal source. there are many circuits hobbyist can use from specialized IC (like ICL8038, XR2226 etc.) to a generic version that uses OpAmps for example. in addition to having oscillator, it is important to have attenuator so you can reduce amplitude of the signal down to few mV for example (potentiometer will do).