Smell: GT85, unsurprisingly.
Sound: The 'click' of an M735 thumbshifter, followed by the slight 'chink' from the chain as it slips across the cassette. Made me smile only a couple of hours ago as I rode home from work.
Sight: Deore DX, any of it, on any bike, beautiful.
Taste: The unique gustation of a bottle topped up with fresh water, but not cleaned since the last ride.