Perhaps:
Use it to inject an audio portion of an RF signal in a RF generator. Through modulation port. Many RF signal generators do not have a modulation unit built in, but do have a BNC for injecting modulation. You then get an AM signal for testing receivers both AM and SSB. Some RF generators will also modulate to FM.
Use it to design switched mode power supply, these things frequently use 100 KHz frequencies.
Use it as a microphone input to test radio transmitters, more reliable than shouting into the mic.
Use it to test speakers and headphones, and the audio response of audio amplifiers.
Use it to drive the neighborhood dogs nuts with the correct dog whistle frequency.
Test your own hearing using different frequencies
See if you can shatter glass.
Maybe an ultrasonic cleaner? These things usually require a big signal however. And a transducer.
See if high frequencies in an office environment make people nuts.
Turn an arduino input on and off rapidly
With the correct phasing maybe learn to "cancel" certain frequencies.
Use it to check the performance of capacitors and inductors at KHz frequencies.
I am not advocating any harm to anyone, just pointing out some of the applications of an AF generator. Also some of my suggestions may not be entirely practical.