Without any fanfare here is my current list of things I want Shopify to be able to do. With luck, I'll be removing items from the list faster than I'm adding them.

1. Ability to set the current language (translation) using a querystring. Just like we can view the alternate templates. Whilst this won't offer a full translation at least the main items in the theme will be.
2. Ability to grab an article in Liquid via its ID. By handle isn't going to be as useful since that's likely to change more often than other handles.
3. Be able to make use of the data that drives the Best Seller ordering for collections. The data for what makes up a best seller clearly exists, so it should be made available on the product object. How awesome would it be to know that Product X has sold 321 items natively.
4. Let us pick a linklist as the link url in a linklist. This would remove some hackiness from the current submenu approaches.
5. This one is obvious -- Allow devs access to the Discount Code API. So many stores need this!
6. Make the admin search tool search actual sections of the admin. The new design makes it harder for some people to know where stuff is, so the search could remove that problem.