How 'bout the wooden acting in Phantasmagoria 2: A Puzzle of the Flesh?
Sadly, I never got around to playing that one.
How about the Tex Murphy
series? The only one I played was Martian Memorandum
, which I quite liked. The "acting" left something to be desired.
Here's a small clip:
Of course, it could be worse. The game tried to emulate human speech through the computer's internal speaker (these were the days when sound cards were still a novelty). It sounded like a scrap heaping trying to belch the alphabet.