[IDA](https://www.hex-rays.com/products/ida/) is one of the more powerful and useful disassemblers. However, it's not easy to get a copy with arm64 support at this time, and is also quite pricey.

[Hopper](http://www.hopperapp.com) is a great disassembler, albeit missing some of the features which make IDA has. Quite affordable for the average person, and demo is very useful as well. 

[Capstone Engine](https://github.com/aquynh/capstone) is a open source disassembler. Hopper uses CE at its core. This one is totally free,with multiple bindings,can be integrated in your own projects,however, you might have to write your own binary loader for it

Hopefully going to get [qira](https://github.com/BinaryAnalysisPlatform/qira) working on iOS. Would be incredibly useful for analysis.