My favourites:
"We're dead, Alan." The way he says it is priceless.
Gideon screaming 'Oh My God!' at everything.
Barry in general was brilliant, though there were two moments that really made me laugh:
Barry trying to convince Sly Hands to drink the Freeze potion.
"Does it taste of alcohol?"
"Well, more or less."
And also when he's with Rothberry near the beginning.
"So will you swap that potion?"
"Well, if I'm honest I'd rather swap the lamp."
I also thought Matt from S6 was a laugh as well, especially his overdramatic flail when he fell off the causeway and his team posing at the end.