I‘m having alot tools sitting in my Blender, but what I regularly use, nearly for every work, are these:

• Extreme PBR Evo (paid)
• Gaffer (paid)
• Cycles Material Vault (paid)
• Material Library (free)
• Simply Cloth Pro (paid)
• UV Squares (don‘t remember but someone here said it‘s free)

Other addons I use from time to time:

• Kit Ops Pro (paid but there‘s also a free version IIRC)
• EV Express (paid)
• Pro Lighting Studio (paid)
• Wireless or Cablerator (paid)
• Extra Lights (paid)
• MDTree (free)