LTC? I actually like it quite a bit. It's kind of the under-appreciated little brother of Bitcoin. It's faster, and I think there will be plenty of merchants who choose it over (or in addition to) BTC for that reason. Currently, the main factor in Bitcoin's dominance is just acceptance level. But, assuming cryptocurrency eventually reaches mass adoption, there may be quite a few cryptocurrencies which have more than enough adoption level for the purpose of merchants. At which point, efficiency and fees will be a larger driving factor.