Probably like many others, I have a collection of discount codes from various online shops that are lost in the depths of my mailbox. To remember I have them - and to actually find them - is a pain. The Autofill functionality of LastPass could be re-used to store and autofill discount couponcodes/ vouchers as well. Include something of an expiration date to the code and it deletes/demarks it at that time automatically. I imagine it would work fairly similar to the password side of the solution. Only you can have multiple codes per webshop and add an expiration date.
I know this is outside the core business of LastPass but could greatly differentiate the solution from others. Online I haven't been able to find someone that does this and it feels like a relatively easy to built add-on with great impact on customer experience.