I already brought this up in part on the Events thread, but there are certain plugins that I see as core plugins: Membership, ProSites and Marketpress.
For Marketpress, I think there are a lot of smaller plugins that could be better handled as extensions to Marketpress.
My wishlist would include
– Group buying
Requirements would be adding the ability to set a minimum number of purchases for a product to become available (the ability to easily refund any purchases if the minimum is not met would probably be the way to work this out as far as payment processing), ability to set a maximum number of purchases. Not so much a Groupon competitor as a way to allow people to run their own deals.
– Time limited deals or products
The ability to limit availability or price of a product by date and time. Should be able to be combined with group minimums/maximums
For reasons already described, I think that would function better within Marketpress