UniCoin
Unicoin is created by combining a certain amount of coins. Maybe based on their total finite amount or market value at the time.
So it could be 1 BTC, 4 Litecoins, 10 BBCoins, you get the idea. To create 1 UniCoin.
In this process, the normal coins are destroyed and you are left with a coin hash which is calculated from a combination of these coins. This will slowly kill off the "normal" coins.
To counter new altcoins, they will successively be integrated into Unicoin. So over time, you start adding Feathercoin, Chinacoin, whatevercoin etc.
So there would be an incentive for early adopters, as it would require more and more coins to craft a UniCoin.
If you want to "mine" an UniCoin, you simply need to first mine 1BTC, 4 LTC, etc etc. So it is technically mineable, but by mining each separate currency.
The idea is by using this method, you will leverage all the altcoins into one single coin, making it pointless to invent useless clones, while also utilizing a bit of every coins improvements.
Someone make it happen
Basically, it requires manual labor, sending an amount of bitcoins to an address that would be extremely hard to compute the corresponding Private Key, like the BitcoinEaterAddress, based on the tx, you have the proof and input the raw tx, or just the hash of the tx and hash that.