I was thinking about the best spells of every type (best level 1 slow, best stun, best damage), so I compiled a small list waiting for the patch. (I probably should define best because range and channelling come into play, obviously DK's dragon tail is the longest stun, but has terrible range and is not efficient at level 1, but I put it up since it would probably be discussed anyway; other examples of this problem would be AM blink and QOP blink, neither want it level 1 like Earth Spirit does).
Add any categories that you don't think are covered or any spells that belong / don't belong up here.
Best Slow:
- Kotl-Solar Bind
- Enchantress-Enchant
- Warlock-Upheaval
Best Stun:
- Dragon Knight-Dragon Tail
- Mirana-Sacred Arrow
- Leshrac-Split Earth
Best Damage:
- Shadow Shaman-Ether Shock
- Jakiro-Dual Breath
Best Movement:
- Earth Spirit-Rolling Boulder
Best AOE/DoT:
- Sand King-Sandstorm
Best Poke:
- Enchantress-Impetus
- Venomancer-Poison Sting
- Ancient Apparition-Chilling Touch
Source: https://www.reddit.com/r/DotA2/comments/mkwj8l/best_level_one_spells/