Once you reach a certain size most can feel a bit like an aircraft hanger (Manchester’s O2 Victoria Warehouse is the best one of them that I’ve been to). Leaving aside somewhere like Glastonbury as it’s all about the setting, I’ll go with:

The Royal Court in Liverpool - it’s small enough that, wherever you are you get a great view of the stage. It’s where I’ve probably seen most bands too: Rage Against the Machine, Cypress Hill, The Fields of the Nephilim, Robert Plant, Stiff Little Fingers, etc, etc. So, yes, nostalgia likely plays a role.

Not really a “venue” but ever the fan of the beer tend at folk festivals. Good beer and half the musicians just sitting around of an evening jamming.

The Chameleon in Nottingham, Boom in Leeds :)