A Chinese character not pronounced in any of the standard tones

Chinese characters are normally pronounced in one of four standard tones (five, counting the neutral tone).

There is, however, at least one character which is commonly pronounced in a style which differs from any of those four (five) tones. I've heard it often enough in (melo-)dramatic moments in movies or TV programs. If you've seen your share of those, you might have heard it as well.

The mystery character?
唉 (formally āi)
It's a sighing sound, and is often pronounced in a slowly falling tone, typically accompanied by the exhalation of breath commonly associated with a sigh.

One of my dictionaries gives "(an interjection of regret or disgust) alas"; my feeling is that it is more frequently a sigh of regret than of disgust.

Another of my dictionaries gives the fixed phrase 唉聲嘆氣 (āishēngtànqì) to sigh with distress; to moan and groan. In a context like that, where it is not someone's actual sigh, it would be pronounced in its formal first tone.

Tutoyer, vouvoyer

In the late 1980's, I had a French conversation with an American friend who had a wonderful French accent (she had married a Frenchman and had lived in France for some time). At one point she cut in to tell me, "Tu peux me tutoyer." ("You can use tu with me."), introducing me to an infrequently used, but still quite useful verb.

Tu is the familiar form of "you", while vous is the formal form. My belief is that it is fairly natural in an initial French conversation between two speakers, at least one of whom is an adult, that the younger (or perhaps somehow "newer") person would use vous to address the other person. I hadn't previously imagined that there were verbs dedicated to usage of tu (tutoyer) and vous (vouvoyer [not "vousvoyer"]; subsequently realized this sounds the same as Vous voyez ["You see"]).

More than a decade later, I was giving a 2-hour ride to a polite young Frenchwoman (from Martinique, actually), who began by using vous to address me, and switched to tu after I took what may be my only opportunity in this lifetime to legitimately remark "Tu peux me tutoyer.". That car ride was a wonderful, unexpected chance for me to have some French conversation practice.

I suspect tutoyer is used rather more commonly in spoken conversation than vouvoyer, since it strikes me that one would more commonly tell another person that "You don't have to be so formal with me." than the reverse.