I don't think Fallout 3 gets that much credit when it comes to it's writing. Yes, Fallout New Vegas is probably the best written out of the modern Fallouts, but Fallout 3 definitely has it's clever moments.

My favorites are:

From Operation Anchorage, when finally talking to General Jingwei - "I'm going to kill you SO MUCH."

The bluntness of this dialogue choice makes me laugh every time I read it, maybe because of the situation you're in.

From Bill Wilson - "Family first! And any man who anything different is saying something wrong. And you should hit that man. With a stick."

Yeah! With a stick!

What are your favorite quotes?

"uh hey who are you"
"Im the king of the wasteland" or "was thinking of starting some fires maybe killing some people".

I also think all of the dialogue in the quest to get the ghouls into tenpenny tower with the residents is hilarious.

Also from the pitt that Wild Bill discussion was topkek.

My favourite quote from Fallout 3 is:

"Gaarrryy"

Heheh I think you guys know what I'm talking about.