I've got a couple of the little blue Merc drain plugs that are so tight that I can't even budge them. Tried to get at them with pliers but they are either still too tight or there's not enough room to maneuver. Is there any quick trick to getting these things out?

I have always removed mine when the engines are warmed up, I am not sure if that would help.Either way they dont need to be that tight because they have a rubber o-ring that does the sealing.Could you try a small adjustable wrench or open end wrench on the wings.

Are you talking about block and or manifold drain plugs? If so, reverse threaded I believe..As stated above, I use a 1/2 open end wrench over the wings.