The dot-on-the-screen was the hardest for me, as the rest of my testees were hopeless. The machine went 'beep' when the dot was outside the box IIRC, and I had an aural deluge of beeps around me. I wouldn't be surprised if this was intentional.
The interview questions were very tricky too. I remember being asked what I would do if I arrived in my hypothetical strike Jaguar at my nuclear target to discover the aiming point was a primary school playground.