I love the one you mentioned from PC narnianerd!
That is one of my favorites as well.
I know there is a better one, but I'm having a hard time thinking of one that is a movie quote and not from the book used in the movies.
"I like in the LWW Extended Edition when Peter says "Well she's faster then she looks" when Mrs. McGrady was following them.

"Things never happen the same way twice, dear one." -Aslan

"We may never know what would have happened." -Aslan to Lucy

I really like the second quote. Sometimes when bad things happen to me, I often go into a state of "What could have happened if I/we did something different? Then I think back to this quote.

Haha. That may be my favourite line from the entire film series, nn. XD From LWW, Susan's and Mrs. Beaver's discussion while packing is a hilarious breather in an otherwise tense scene (vaguely reminiscent of Legolas and Gimli's banter in The Two Towers). The culminating line is especially amusing, seeing as how I once had such a similar repartee with my little sister.

Susan: Do you think we'll need jam?
Peter: Only if the Witch serves toast!

On a more serious note, in PC I liked the bit of dialogue below. It was one moment where I felt the longing for the old Narnia most heavily.

Lucy: It's so still.
Trumpkin: They're trees. What do you expect?
Lucy: They used to dance.

Good point about Aslan's quote on happenings, Leah. It's so easy to get caught up in "What ifs" when we should be asking "What now".

There are so many great quotes out there that it will be hard to choose!

*Susan finds a chess piece in the ruins.*
Edmund: Hey, that's mine. From my chess set.
Peter: Which chess set?
Edmund: Well I didn't exactly have a solid gold chess set in Finchley, did I?

As much as I couldn't stand the whole Susan-Caspain thing....
Prince Caspian: I wish we had more time.
Susan: We wouldn't have worked out, anyway.
Prince Caspian: Why not?
Susan: Well, I am 1300 years older than you.

I feel like VDT (even with all its errors) is being under repersented here
Desk man: Are you sure your 18?
Ed: Why, do I look older?
Lucy: Edumnd, you promised you would help me with the groceries.

While I'm ambivalent to the idea behind the scene at the registration, this line cracks me up:

Registrar: Alberta Scrubb?
Edmund: It's a typographical error. It's actually Albert A. Scrubb.

XD

^ Ha! I forgot about that part- Narnian_Badger . I wonder why on earth Aunt Alberta would have signed that!

Here are some form LWW:

Mrs. Beaver: You've been sneaking second helpings, haven't you?
Mr. Beaver: Well, you never know which meal's gonna be your last. Especially with your cooking.
(I loved the beavers )

Fox: Forgive me, your Majesty.
Jadis: Oh, don't waste my time with flattery.
Fox: Not to seem rude, but I wasn't actually talking to you.
[looks at Edmund]

But the 100% winner of best Narnia moive quote belongs to Peter

"For Narnia, and for Aslan!"

On a less serious quote, I think this one quote in Prince Caspian is rather humorous.

"If we are to take a vote, I'm with him." - Caspian X to Nikabrik and Trufflehunter

I don't know, but the timing of that line just always cracks me up.

King Miraz: Tell me, Prince Edmund...
Edmund Pevensie: King.
King Miraz: I beg your pardon?
Edmund Pevensie: It's King Edmund, actually. Just King though. Peter's the High King.
[awkward pause]
Edmund Pevensie: I know, it's confusing.

That one always makes me laugh!
Another one of my favorites is:

Lucy: I wish you'd all stop acting like grown-ups, I don't think I saw him, I know I saw him.
Trumpkin: I am a grown-up.

That's all I can think of right now, I might have more later though.

One I've always loved:

Lucy... I think I believe you now...

~Riella

Keeping with the Edmund tune, I've always loved this one...

"The last time I didn't believe Lucy, I looked pretty stupid"

It shows that he's matured since LWW and is now at a point where he can use his past mistakes to help in the present. This is also evident in HHB and VDT.

If he tells us to hurry one more time, I'm gonna turn him into a big, fluffy hat.

~Riella

More of Peter and Edmund, these two are like Quote machines.

"Ed, you've always been there for me and I've never really - OOWWWWW"
"Save it for later"

This is the line in PC where Peter realizes how stupid he was being and he grows up really quick. I love character progression, so I'm a huge fan of this dynamic sub-storyline.

Who's Aslan! You cheeky little blighter!

I don't know about anyone else, but I found that part hysterical.

~Riella

"The last time I didn't believe Lucy, I looked pretty stupid"

Pretty much everything at came out of Edmund's mouth in PC was spot on. Say what you will about the rest of the characters, but I think TPTB did Edmund very well.