Off the top of head:
1: Leonardo, that woman and ferret are worth the wait.
2: Pipilotti Rist, makes video art seem not boring.
3: Marlene Dumas, in the flesh
4: Cezanne at the Courtauld, you need to see them to undersand 20th century painting
5: Tracey Emin, awful reactionary person (tory friend and drawing prof at RA), art not so bad.