The use of ‘in’ and ‘on’ for various vehicles in English is one that I always find interesting. Like you’re on a motorbike, or a boat, or a bus, but you’re in a car. Aeroplanes I think are kind of interchangeable.

Also the order of descriptive words for things is one I really find odd. “I’m on a big red old-fashioned London bus” = coherent sentence. “I’m in a red London big old-fashioned bus” = nonsense.

Apart from that, try explaining to a learner why “Read” (present) and “Read” (past) is spelled the same but pronounced differently.

Also how something like the word ‘jam’ can mean a fruit preserve, a door that’s stuck, traffic that’s not moving, playing music or cramming something into a hole lol.