This, with my Hantek DSO5102P (Ebay £170 with shipping) has added the bare min requirements of a hobby electronics tinkerer to get anywhere in understanding electronics to any meaningful degree for the £20.99 cost and removed the hassle of using a PC with sound card outs, FLS or other wave generator software – which used to be very inconvenient at times for testing valve amps.
With a BNC lead to croc clips you can attach to most inputs like amps etc. to see fixed frequency responses and do general testing. It kicks out about 17Vpp of sine, square, ramp and triangle at 999,999 kHz maximum (1Mhz) via the LCD display and controls. Pretty good for the price.