Re: Three Tuvok episodes - Meld, Gravity and Riddles.
Another Tuvie episode I liked a lot is "Innocence". Not only did the epsiode deal with aging (something they were unwilling to explore with Kes' character but that's another topic) but I enjoyed the interaction between Tuvok and the "kids".
My favorite line:
Child: "Mr. Tuvok, what are your children like?"
Tuvok: "Well behaved."
A Tiger doesn't loose sleep over the opinion of sheep.