Grossly underused words

Ululate makes me think of undulate, to move in a wavelike fashion. I tend to use that one whenever something needs to move back and forth in a portentous way.

Speaking of which, portentous is another good one. I always thought it was odd in that it could mean both ominous and favorable (i.e. a good or bad portent).

Muckrake is fun to say, but I hardly ever get to use it. It means to search for and/or uncover corruption and scandal, so there's always a need for it.

Another one I've been meaning to use more is unctuous, which I first saw in Sam & Max (a great vocab builder, by the way). It means greasy or unpleasantly polite, so there are scads of great uses. I guess scads is a fine word too.

Jam it back in, in the dark.