One case that stands out in my mind was a 12 year old boy, who's natural father had died in a motor bike accident. (his mother had separated from the father and re-married some 8 years before).  The boy was grieving, and acting up at school, and just generally being very hard to get on with,
angry, etc.

The mother brought him to me for a session, and I would have to say he was probably about the most reluctant client I have ever had!  As I have had 5 sons of my own, I was able to get a kind of rapport with him, and just said if he wanted this session to hurry up and be over, all he had to do was mirror what I was doing (no words needed) and he could be out of there!
He actually complied and you could literally see the change in attitude within 10-15 minutes or so.

His mother kept in touch and said the behaviour improvement was amazing.

Another little boy, a 5 year old son of a client, was really miserable at having "no friends" at school - so I had him tap for

 "Even though I'm not very "POP-UL-AR" (his way of saying the word), I'm a real super-boy" -

this worked and his mother also reported a very positive change in attitude for the better.