HighRes image crop tool (not Aviary plugin)
Aviary is pretty heavy handed. I agree with you, it'd be great to have some tools in Craft to handle cropping. There's been some rumblings in the past of Craft 3 shipping with some new toys but that's a ways away. I don't know of any alternative but you could certainly build your own.

Use something like Jcrop then use some tools server side to crop the actual image. That's relatively straightforward.

Implementing it in Craft is the other tricky piece. Wonder if anyone else in the Craft community has tried doing something like this?