"Chocolate?"
By far. The best. Scene. Ever. The best part was the look on Lenoard's face right after it happened for the first time. When Sheldon offered her it I immediately went "Oh.. OH NO." Although I will have to say that Wil Wheaton pulled off a MASTERFUL scene for not having been on TV for awhile. Although looking at his IMDB I see he did some show called leverage.
I also found the scene where Raj is talking to the group and Penny is outside the door pretty touching. Yes, it was played for laughs but it kinda got me how real it was that not even he understood his disability.