Richard Griffiths as Vernon Dursley

Probably some of the best casting in the series. He acts exactly like Vernon, and he even has the appearance (save for the hair color, I believe).

I watched Philosopher's Stone a few days ago again, and I really thought Griffiths is an excellent Vernon Dursley... He had that mad gleam in his eyes when the post starts to arrive...

Yup. Richard has the best facial expressions as Vernon:

http://bloghogwarts.com/wp-content/uploads/2008/03/normal_vernon.jpg

So, I was watching Order of the Phoenix, and I remember the scene that made me love Richard as Uncle Vernon so much more: after Harry comes into the house with a sickened Dudley, we see him near the fridge with a spoon in his mouth and some ice cream. :P

Griffiths looks pretty much like I pictured Uncle Vernon. The only thing is that he slips up once in a while and is almost nice. :)

Griffiths was a spot-on casting decision. Just excellent. He hasn't had as much to work with in the recent movies, but he absolutely shined in the first two movies because he just nailed Vernon Dursely. I would say he's one of the best cast characters, but almost all of the adult characters were perfectly cast and Griffiths was no exception.