Hey Halono!
What makes this coin special im my opinion is its collaboration with charities and usecases toward charities. I know of no other coin with that particular direction. This combined with a talented dev and an active community is what makes me believe in RAP.
When it comes to masternodes and what they do, I think the main functions are instantsend (fast verification), cloaking (anonymizing transactions, not quite sure about this one), community voting systems.
Another feature of rapture is the wallet service it provides on masternodes. It offers servers for running masternodes both for RAP and other coins at a low price, and with a much easier setup. This is called the hot-wallet-service.
Have a great day!