Hubitat's Generic Z-Wave Switch (and Smart Switch) driver implements a flash() command, though if it's the same as the example driver they've published in their repo, it's basically faked at the software level by switching on and off repeatedly. Mysteriously, the Generic Z-Wave Outlet driver does not include this same command. I'm not sure what the differences are between these two drivers (beyond this) other than the fact that one includes preferences toggle the LED indicator found on most switches as well as a preference to reverse the paddle direction, both parameters not likely found on a Z-Wave plug. If you don't try to use those, I'd guess there would be little harm in using this driver instead of the outlet driver for nearly any Z-Wave smart plug. The situation is similar on the Zigbee side, where the Generic Zigbee Switch driver implements this command, and the Generic Zigbee Outlet driver does not; again, I suspect you could probably use either. This would include the Peanut Plug, though that is not an officially supported device (but many people have it working).
At the bulb level, the Aeon Smart Bulb 6 support some sort of flash capabilities according to its documentation, but it's not clear to me exactly how that works. I'm not aware of any others that do (the Generic Zigbee Bulb drivers do not expose this as even a "faked" command, and the Hank, Yeelight, and Hue Bridge bulb drivers do not implement a command for this, either--though I wrote a custom Hue Bridge integration, CoCoHue, that does, and the Hue B Smart port does as well).
Unless the bulb/switch/outlet supports something like this natively (Hue sort of does, a "long select" command that flashes the bulb 15 times, or a regular "select" that flashes it once, neither exposed by the stock Hue Bridge integration), then the "emulated" flash is nothing you can't do yourself with something in Rule Machine--something like Capture State, On, Delay 1 Second, Off, Delay 1 Second, On, Delay 1 Second, Off, etc., and a Restore State (or not if you want to define how it ends--on or off). Doing this a bunch of times in a row probably isn't great for your Z-Wave network bandwidth, but it apparently wasn't enough to stop Hubitat from doing in the stock (or at least example) driver that way, so it's probably not too bad. 
