Its gotta be take-off on a Rolls Royce powered 757 - that growl!!
767 is pretty similar at doors 2
The 767 also makes some pretty interesting noises at doors 3 (300ER) when the flaps/gear are in transit.
The 1-11 used to make a classic high pitch whine during start, as of course the deep penetrating hum of the TriStar.
The DC-10 is interesting too, if you sit at doors 3 , it makes an almighty whooshing sound on rotation,the sound of v fast airflow.
I like the hum it makes during taxi too
The 777's interestingly quiet, but i prefer something sounding powerful !