I actually used this today in chem. class when I forgot to bring in my packet (of all the topics for the unit), it just popped into my head, then when she asked where my packet was I said it.
The dumbest excuse ever is...
"Oh my (insert thing here) is on vacation, I heard it will be back tomorrow"
I shit you not I used this today when it came out of my ass.
My teacher replied "right... Just get it to me tomorrow"
don't flame :)
edit: holy crap, my 1300th post!