Have you made a call to a large corporation in the last... oh... two to fifteen years and had a positive experience in which you were waited on promptly without a number of transfers and without having to repeat the same information ad nauseam? Did the employees seem to want to resolve the issue about which you were calling? Yes? Do you have four legs, a silky mane and a single, pointed horn growing out of the top of your head? I thought as much. (NSFW language) -Via Viral Viral Videos
Coming in second is Amazon Prime. They completely avoid customer service by allowing the return of anything.
I rarely have to ring big firms - perhaps I'm just lucky, but my experience has (generally) been good.
Except Virgin Media, who plainly lied to me when they said they were charging £20 installation charge for a new modem when I was installing it myself. Then, when challenged they said it was "shipping"...just bollocks, frankly. On the other hand - the modem arrived and worked without snags.
On the other end of the spectrum, I always had awful support with Dell and even calling from a business with service contracts. The worst was the time I spent four hours talking to three different techs trying to convince them they had a mistake on THEIR END. They mis -matched a product with a replacement part, wrong size for an all in one monitor and pc stand, and they claimed they couldn't just send me a new monitor just the same wrong sized AIO part that the pc wouldn't fit into. Never managed to get the correct part.