something simple like a drill or table saw youre OK with leaving plugged in, but anything with electronics,like speed controls or computer control crap on it leave it unplugged when not using it so surges and voltage spikes won't destroy it..we had a concrete forms truck hit a power pole here out on the road and the pole top broke off with lines at 33,000v dropped down onto the 13,000v below that feeds our road and fried a lot of stuff up and down the road..took out two pole mount transformers,three surge suppressors here and killed a fridge..my auto drain control on my shop air compressor is fried too but I didnt find out till weeks later..
I keep everything unplugged as much as possible 'cause you cant get anything from the power co for the damage