Open Source Gems

GEM for Frame Animation.
Open toonz is unbelievably powerful, has both vector and raster animation and you can use mypaint brushes for variation in frame work.
Another software where the interface is quite dated though, there could be a lot of work in that regard.

GEM for Scalable Vectorial Drawing.
Runs more Smoothly by each version that comes. Can't wait for 1.0, looks pretty as hell.

GEM on Office Suite Applications.
Powerful features - good interface design, easy to use and a good range of applications. A total beast.

GEM for Digital Audio Workstation
The interface is still very complicatd, but still very powerful.
Used along with Audacity is amazing.

GEM for audio recording and editing.
Along with LMMS you got your own studio going, pretty muhc. The intercae is very dated and could use an update, or at least support for Community themes.

GEM For Digital Drawing
Krita has a lot of features, the brushes defaults that come with it are very good and it runs very smoothly even with Drawing Tablets (no jitter, or delay).

GEM for Photo/Image Editing.
Tons of features - Interface could use improvements and the latest update is a step in the right direction in that regard.

GEM for 3d Modeling
2.8 Is a blast, runs smoothly and the interface is just amazinggly well thought.
Wish they could work more on the sculpting workflows though.

GEM For Spine Animation
Defenitely needs to be more known by the comunity, the software is very powerful but lacks comunity envolvement/tutorials.