A suggestion for one of the first apps is blockchain based dice.
It should be fairly simple, while demonstrating the ability of LSK to earn revenue and it should drastically increase transactions, a metric often used to measure blockchain growth/value.
JustDice for example had a bankroll of > ฿50,000 & was earning >$300 000 profit a month until it was forced to close due to regulations. A fate, a decentralized blockchain won't succumb too.
http://www.bitroll.co/just-dice-closes-due-to-canadian-bitcoin-regulations/Also by comparison when BTC was a similar size to LSK with a $70 million CAP in 2012 online gambling accounted for nearly half of all BTC transactions.
http://www.forbes.com/sites/jonmatonis/2013/01/22/bitcoin-casinos-release-2012-earnings/Satoshi dice had nearly 1.8 million BTC worth of volume and BitZino 700 000 BTC, so probably about $30 million dollars turnover & I think there were about 6 million betting transactions.
A really low house edge, provably fair, funds accounted for on the blockchain option could displace Bitcoin options which have recently been hit by a string of 'ponzi' take the money and runs...
In order to rapidly accelerate LSK value it needs to be seen to be pushing out DAPPS faster than competitors so that the market can see javascript is both more popular and easier than competing alternatives.