'Sweetest' use cases? Well that depends on who you ask, of course.
IMO, the value proposition of Bitcoin's underlying protocol is enormous. You can strip away the coin and manipulate the protocol for alternative use cases, such as carbon dating (voting, prior art, etc...) [1], carbon emissions trading platforms [2], the preservation of open data [3], reputation scoring for TTPs [4], messaging systems [5], decentralized asset exchanges [6], etc...
As for more traditional use cases Bitcoin obviously shines in bankless states with weak national currencies. In the same vein Bitcoin offers protection from seizure of funds during bail-ins and the like. In the context of donations Bitcoin is awesome as well; without Bitcoins wikileaks would have some trouble accepting donations. The list is endless, really. Every use case is powerful.
IMO, the value proposition of Bitcoin's underlying protocol is enormous. You can strip away the coin and manipulate the protocol for alternative use cases, such as carbon dating (voting, prior art, etc...) [1], carbon emissions trading platforms [2], the preservation of open data [3], reputation scoring for TTPs [4], messaging systems [5], decentralized asset exchanges [6], etc...
As for more traditional use cases Bitcoin obviously shines in bankless states with weak national currencies. In the same vein Bitcoin offers protection from seizure of funds during bail-ins and the like. In the context of donations Bitcoin is awesome as well; without Bitcoins wikileaks would have some trouble accepting donations. The list is endless, really. Every use case is powerful.
[1] CommitCoin: http://eprint.iacr.org/2011/677.pdf
[2] CarboCoin: https://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=64683...
[3] http://btcgsa.info/wp-content/uploads/2013/07/Decentralized-...
[4] https://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnum...
[5] BitMessage
[6] BitShares, MasterCoin, Freimarkets