On my climb to Pro Rank I mostly used a weird MO deck running GN, Tome and insects and a radical 5-10 Mutagenerator deck with Geralts and Cintrian guard.
I must say it was lots of fun. Facing NG Renfri and SK Raid with them not having a clue what comes next was really beneficial and made me totally enjoy the game! Never faced a mirror at all and most people had no clue what/ how to counter the strategies.
What are your weird/ off meta decks you've been successful with?
Edit: Since I had a few PMs regarding the lists – here they are:
Mutagenerator:
Nekker Tome:
Source: https://www.reddit.com/r/gwent/comments/zafepn/success_with_offmeta_decks/