For me, it's the 'Just In Lust' b-sides. This was the point where I went 'Whaaaaat? Holy shit! This is everything I've been waiting for!' as they assauged the (mild) doubts I had after hearing PHUQ (Despite 'I Wanna Go...' being one of the most deceptively profound/ transcendent songs I'd ever heard).
'Mindslide'/'Friend For 5 Minutes'/ 'Sin (in sin)' changed my fucking (musical) life and outlook. 'My heart's in the song, but my head's in the battle....' Life's joys celebrated and its vicissitudes condemned within a couplet. Set the stage for the rest.....
The 'Caffeine Bomb' b-sides run a close second, though. 'Shut Your Fucking Mouth....' represented the often misunderstood/ignored intelligence of the band; in a way that would be routinely misunderstood/ignored, while 'And The Bullshit...' was the most articulate poison-guitared hate-mail message to a record company I'd ever heard (and still have heard to this day). And all the while broiling with the sheer joy of melodic rock'n'roll invention. Meanwhile, 'Girlfriend Clothes ' was in the mould of Pulp's social satire, if only Pulp were capable of truly rocking.
You?