I don't know: fuzz bass, guitar feedback, orchestral pieces in a rock song, the "concept album", reverse guitars/vocals, countless other studio tricks. I read Geoff Emrick's book "Here, There and Everywhere" and he goes into great detail on the new ground the Beatles forged.
Interesting to me too reading about it, they would create/introduce something new like a tape loop, use it on just one song, and then move on. Where other bands would define their entire sound by just such a novelty.
The thing is, people tend to exaggerate how many of these the Beatles actually were first with. For example, here's fuzz bass from 1961[1], and another instrumental from 1961 with a lot of fuzz[2]. Both by Grady Martin, who's hardly a household name.
There was a lot of musical experimentation during this time period coming form all over. There's a tendency to collapse all of that to just a few popular bands, and then pretend they're the lone geniuses who invented everything.
It is true but consider also that whoever made the first song with a new tech which became popular actually was the first to truly make it work well enough to make it popular.
Interesting to me too reading about it, they would create/introduce something new like a tape loop, use it on just one song, and then move on. Where other bands would define their entire sound by just such a novelty.