A lot of old jeeps used to have PTO ports on the transfer case, so you could use the jeep engine to power machinery. I suppose you could do the same thing with modern vehicles, at the cost of some mechanical complexity.
A more interesting option on EVs would be a big switch to disconnect the 3-phase AC motor from the motor controller, and route the power to an external plug with three conductors and some sort of control interface. The idea would be to use the car's motor controller as a programmable power supply for just about anything. You could have it generate normal 50 or 60 hz AC power (single phase, double phase, or 3-phase) at any voltage up to the pack voltage, or it could supply DC, or it could act as the power supply for an arc welder, or it could act as a motor controller for just about any kind of motor (with the control interface used to update the motor controller on the motor position, for motors that require that sort of thing).
There's this problem generally with electrically-powered devices like electric lawn mowers and chain saws, that they're limited to about 2 horsepower because that's about the limit of what you can send over a 15-20 amp circuit at 115v AC. 220V AC gives you more power for things like big table saws, but there isn't really a standard for 220v household extension cords, as far as I know. But a typical EV motor controller (or the battery directly) can supply hundreds of horsepower worth of electrical energy. It's kind of scary, actually, when you think about it. You could power a lot of stuff with that, if we just had interconnection standards.