He had so many great moments that is hard to pick one...
In the DH: "You are joking, Perce!" shouted Fred, as the Death Eater he was battling collapsed under the weight of three separate Stunning Spells....."You actually are joking, Perce....I don't think Ive heard you joke since you were-"

"The thing about growing up with Fred and George is that you sort of start thinking anything's possible if you've got enough nerve." - Ginny

YouTube - Brothers Forever ~ A Farewell to Fred ~ (There You'll Be)
YouTube - Fred Weasley- Tears in Heaven
YouTube - Fred Weasley: Hero till the End

Dang why did I have to watch Pips video and all off the above... Now I am crying...