Simple way to create 10 volt square pulse?

I'm just looking for the easiest way to create a sketch/circuit like "blink" but that pulses 10 volts instead of 5 on an arduino mega2560.

What load will it be driving?

Very little --maybe 10mv. It's to drive a tachometer gauge.

Simple way - take 10V source and chop it up.
Use an NPN transistor to drive base of PNP transistor.
PNP has pullup resistor from base to 10V to turn it off, and NPN pulls base low to turn it on.
When PNP is turned on, it sources 10V to the load.
If source is 12V, the PNP output will be a little lower, and can put another diode or two get down in the 10V range.

10mV is not a load - perhaps you meant 10mA.

Thanks and yes mA of course.