Propose at the place where you first met.
If you're both musicians, play a song together.
If you're both writers, write each other a letter.
Hire a skywriter to write Will you marry me? in the sky.
Hide the ring in a piece of cake or a bottle of champagne.
Take her on a scavenger hunt that ends with the proposal.
Tell her how much you love her and why you want to spend the rest of your life with her.