Not helpful for the OP, but everyone in my group was shaking our head at Skywrite. The only use anyone could find for it would be to write profanity in the sky, since I ruled he couldn't draw a giant **** instead.
Never seen cast:
1st level - Witch bolt
2nd level - Melf’s Acid Arrow
3rd level - Fear
4th level - conjure minor elementals
5th level - contagion
6th level - arcane gate
7th-9th level - All of them, except finger of death and power word kill.
Always seen, never succeeded:
Banishment - I’ve seen this spell cast a total of 20 times in 5e, by nine different people (myself included). It has never, ever worked.