A funny poem, maybe one you write based on a famous poem that most people at the party will likely know? You could print it on nice paper--suitable for framing--and read it aloud at the party.

For my 50th birthday party, guests were asked to bring, in lieu of gifts, a poem or other reading to share. Some were serious, but most of them were a scream, including the following birthday haiku:
Getting older sucks
Yes, it really really sucks
It really sucks a lot.
(Though I think some liberties were taken with the strict haiku form. )

But everybody doesn't have to be doing that for you to do it on your own--could be fun.