Mac's in-built but largely unknown Grapher app has the best equation editor I've used. Super easier to use, automatic sub/superscripting, and you can right-click to copy as LaTeX.
Makes me sad that Grapher seems to be abandoned -- Apple invests a lot in pro apps, and consumer apps like Garageband. Where's the love for science/math? Surely the market is as large as the market for, say, musicians? There are a lot of engineers/scientists out there.
As much as I love Keynote it'd be sooo useful to have native equation support, and native code syntax highlighting (can't they port this from XCode?)
Apple is slowly pulling out of academia, where they used to shine quite well.
If Grapher ever gets abandoned, I really hope they open source it. An update for the icons to be retina-ready, and moving the backend to Metal, and maybe easier integration into Keynote/Pages, would be all it needs to make a kiss-ass product. It'd be so far beyond anything anywhere else. Can you imagine how nice it would be for students to easily be able to embed/edit mathematical graphs into their documents?
It's crazy, there's a whole generation of people who grew up with graphing calculators, and yet it's such an ordeal to do something similar in Pages or Numbers right now.