Unlike Spock, Tuvok appears to be truly stoic, never showing any outward emotion. Though I'm not a Voyager expert and so I'm wondering if this is truly the case. Instances where Tuvok is being controlled by an alien, or is being represented by a hologram, etc., do not count. Nor does the "Living Witness" Tuvok count, nor Tuvok after he melds with the Maquis lunatic ("Meld").
I think that it can be argued that Tuvok most certainly shows frustration at times, but I'm looking mainly for anger, happiness, sadness, excitement, and so on.