Most sexually charged taboo of the 20s? The communion scene!
Every list of shockingly sexual moments on film seems to focus on graphic and unimaginative stuff like Sharon Stone recrossing her legs sans knickers in Basic Instinct. Cheap and bawdy. Flesh and the Devil made me exclaim "WHOA!" when they were taking communion. The minister turns the chalice an inch or so for each person down the line, but Garbo turns it back to where Gilbert's mouth had been to take her drink. How intimate was that! And in church! Wow.
"A woodcock!" Everyone must see the French restaurant scene in "Deception" (1946). Ah, Claude Rains!