Personally I prefer just volume knob. However, if someone has a guitar with just 1 volume knob and wants to suck some high frequencies out of the pickup signal, there are some simple workarounds.
This is somehow standard wiring with separate tone pot. Tone pot behaves just as variable resistor. The lower is resistance, more treble content is 'sucked to ground'. All resistor and capacitor values are just an example:
Advantage or disadvantage of tone pot is, that it sucks some high frequencies at all times, even on max treble setting. If someone wants to emulate this behavior on a guitar with just one volume knob, it is pretty easy to add a fixed resistor and capacitor:
If someone wants to have fast switching between 'no tone knob' wiring i.e. for rhythm and 'some tone knob setting' for lead, it is possible to implement an ON/OFF switch. Off position is 'no tone knob'. Instead of the switch, push-pull pot can be used. Component values should be chosen experimentally, up to liking. Cap i.e. somewhere between 10nF to 68nF, resistor 0 - 1MOhm. Depends as well on pickups of course.
Here one more example with two fixed settings, where emulated tone knob is connected at all times. Again, instead of a switch, push-pull pot can be used to avoid drilling to precious instrument. OFF position means more treble, as the sum of Ra+Rb takes place. ON position means less treble, as just Ra is active.
There are many options, in the same way caps can be switched, or both caps and resistors... Just one needs to be careful, any component with one disconnected leg should stay connected on it's ground side, not on a side with active signal.