I'm happy I haz you.
Available at: MimosaCards http://www.etsy.com/listing/57201344/cheeseburger-cat-im-happy-i-haz-you-set ($12 for a set of 10)
I'd prefer to write a note on a real leaf with a sharp stick, but that's just me.
Sometimes the simplest ways to say "I love you" are the most effective.
These cute little sticky notes sell for $3.50 at Nothing Elegant.
Inside is a cyclops monster, there to love you forever. I accept!