Here are some Pie Menu-inspired menus created by Simon Schneegans who also created GNOME Pie (haven't tried):
The windowed/stacked grid-based item selector (used in GNOME Pie 2):

The Trace Menu

The Coral Menu

An earlier version of GNOME Pie:
Cool stuff, here is his Vimeo page:
And his GitHub profile:
Edited to add his Github.io page with more information on GNOME Pie and Pie Menu related stuff:
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Also check out Don Hopkins' Medium posts if you happen to like Pie menus:
https://medium.com/@donhopkins