I've thought about this one for days, its hard
The least favorite rod i can think off was a Hardy ultralight 9ft 5wt, that i spent months saving for and had wanted for years having played in the shops with it several times, leering, touching, fantasizing.
I eventually had enough and traded in an orvis trident 9ft 6wt and my then beloved shakepeare president 8ft 4wt, for my 'ultimate' rod.
Still felt awesome in the shop, but what a dissappointment on the water
I was gutted, i kept it for a few trips, never bonded at all and sold it on to finance the purchase of my first 3wt blank, a sage 389LL (which i loved till i tried an XP) the rest is history
The upshot was never buy a rod you haven't cast with properly, a lesson well learned and the reason I'm a pest when someone has rod i haven't tried
But anglers are great people and we all share good knowledge
Sandy