Ok, here's all the guitar puns I could think of on such short notice:
I hope you have a great birthday! (No
"strings" attached) I also hope everyone sings in tune(r), that your celebration takes you to the next
(Fender) Strat-osphere, and that some of your friends take you out to a nice
(whammy) bar. Don't drink too much though, because you don't want to turn into a pain in the
"neck".