Fun with nouns! Well--maybe. I guess it depends on your definition of fun.
While students were sharing their journal entries, I played a little game of "What's My Rule?" We do this in math class to help students recognize patterns. But it is a great grammar activity, too.
I wrote down words from the text as a student read aloud, and then the students had to try to guess the rule for the list. I started out with just nouns, but branched out into common nouns, proper nouns, and plural nouns. After I made each list, students gave the list a name based on the words that I chose. It was a fun way to reinforce nouns AND look at their role in the students' writing.