according to me, the best to invest are:

-Quantstamp : Quantstamp is the first scalable security-audit protocol designed to find vulnerabilities in Ethereum smart contracts

-airswap : protocol for decentralized exchanges

-request.network : A decentralized network built on top of Ethereum, which allows anyone, anywhere to request a payment.

-wanchain : Wanchain is a distributed financial platform that enables private, cross-blockchain smart contract execution

those are definitely the best shots in terms of  profitability and strong concept/development

some have a closed whitelist so you could not partecipate yet.