Defense against d4
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Anything with Kf6 is nice to learn and fun for black, especially the KID or Grunfeld. Even the Volga Gambit is fun
"... the Grünfeld is an incredibly demanding opening, with boundless amounts of theory to cover, and many of the lines are long, sharp, convoluted, and strategically complicated. Therefore, while it has a great deal of appeal because of the pedigree of the players employing the opening, understanding the opening sufficiently well to play it confidently is a whole other story. ..." - FM Carsten Hansen (2011)
https://web.archive.org/web/20140626233841/http://www.chesscafe.com/text/hansen149.pdf
https://www.qualitychess.co.uk/ebooks/GrandmasterRepertoire8-Excerpt.pdf
https://www.qualitychess.co.uk/ebooks/GM9-excerpt.pdf
Try the MacDonnell gambit!
They think you're crazy when you sac your b-pawn, but then bxf7+ and BAM! you've got sufficient compensation!