Teemo & Yasuo Synergy
Teemo Top and Yasuo ADC win 55.5% of 1,609 Low Elo games together, +1.1 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
Playing the duo
Noxious Trap (R) slows and damages enemies but does not knock them airborne; Yasuo still needs his own Steel Tempest (Q) tornado or another ally's knockup to cast Last Breath (R).
Teemo's common magic-damage build and Yasuo's physical-damage carry build give this pair two damage types to defend against. (Unverified: no source confirms this note.)
How to play as Teemo
Set Noxious Traps (R) along the approach to an objective before Yasuo fights there; the slow and chip damage make the route less safe for enemies crossing into his engage. (Unverified: no source confirms this note.)
How to play as Yasuo
Use your own tornado as the airborne trigger for Last Breath (R); Teemo's mushroom slow is useful follow-up but cannot activate your ultimate by itself.
Sources
These notes come from r/TeemoTalk, checked against the champions' abilities.