GRCRTools

GRCRTools is 'the' userscript for browser game Grepolis, which many players can't imagine playing without. 
What started as just a simple report converter, known as GRC (making it possible to share all kinds of in-game reports), 
became a powerful toolset, which capabilities have long since surpassed reports converting:
comparing historic wall data
polissearch
optimized army building
and many more...