Protoshares and Memorycoin(2) run very memory intensive hash algorithms for every cpu thread running on the wallet qt miner it was suggested to have 1 gb RAM.  I believe the OP is looking for something that would be mineable for an average computer that could not be taken advantage of by botnets, and which would take a long time for a gpu miner to be created.  Or be disadvantageous to run a gpu to mine.
(also i know asics memory is on die, im saying it would be a neat feature if a future scrypt n miner was able to put in better memory as needed)