The Shangri-Las, definitely. In terms of the amount of lyrical scope a person can shoehorn into a love song no other music from the 60s came close, they did pacy stuff too but were unusual in that they were at their best doing the ballads. Foreshadowing current trends in metalcore by several decades, not even Bob Dylan attempted anything as emotionally bare as this (and if he did, it would have just been whiny and annoying until someone else covered it, as per usual):
Girl-pop is the best pop, and the most popular girl-pop was The Supremes, this type of thing is what people were really buying in droves back then - believe it or not, apart from a few select bands the rock styles people commonly associate with the 60s were a niche concern that didn't hit the charts as often as you might think. Think about grunge in the early 90s and how few grunge bands and albums actually got good chart positioning and were outsold many times over by stuff like Mariah Carey and New Kids On The Block. Similar situation back then with the rock stuff. The best-selling groups in this style were as big as The Beatles, not to mention prettier, and even had longer careers...
There were of course a ton of these groups, all with huge hits that you'll recognise instantly because your music taste is awesome.
For the rest of you, here's part 1 of a doco you can watch to educate yourselves on the music of the 60s that actually mattered.
