Just use Evernote if you have to. Just delete the list after you are done shopping.
That's not quite the use the original poster was looking for, it looks like the Original Poster was looking for an app that could be a master list of groceries so that multiple people in a family (for example) could simply add stuff to the list as it was needed and then when someone went shopping they just deleted the items they bought so that when someone else went shopping, the stuff that was already purchased would not be on the list anymore and they would only see the stuff that hasn't been bought yet. I would love such an app, but I have not seen one that works this way (if that is indeed what you are looking for) unless you have a family where you all have multiple devices using one apple ID. IF That were the case, then you could simply use the Notes app and make a grocery list in that and as each item was deleted, it would be removed from all the other devices' Notes app