- The Core one is safe, original and has many qualities but has to download the whole blockchain. And so does Armory. - Online wallets are easy to use but unsafe.
In my opinion the best ones to use are Electrum and Multibit but still present some problem.
- To earn Bitcoin ( ... but this is for money in general ) - To buy Bitcoin anonymously. There are PSC and Ukash options, but are too expensive accepted by very few people. - To spend Bitcoin. Few sites accept Bitcoin and almost no physical store where I live.