It's a mix of things. Essay are the easiest because you always get some points. It's not all or nothing. We don't get many of those, though because of the sheer volume of tests to grade. The TA's end up grading them and then you have to argue for points.
True false aren't bad, but they rarely give you one choice. It's always in pairs or redone as a multiple choice.
I find multiple choice to be the trickiest. Your choices are usually, A, B, C, D, E, A + B, C+ D, all of the above, none of the above, etc. You might think a drug choice is correct, but then they will change the dose of a drug from 150mg to 300mg and you'll miss it because your eyes are glazing over by that point.
My favorite are matching. Unfortunately, those are rare.