Haven't seen all of TAR1, so I won't do that, but for the rest of the seasons:
TAR2: 'Confusion Now' or 'Confusion Later' Detour in Thailand
TAR3: EVERYTHING - Derek & Drew's Mexico FF, 'Punt' or 'Bike' in England, Roadblock in Scotland, everything in Portugal, Moroccan carpet FF, Moroccan escargot selling (the only Roadblock goddess Flo ever did <3333
), ABSOLUTELY EVERYTHING IN AMAZING SWITZERLAND, searching for that Singapore celebrity, Vietnamese 'Hard Sell', 'Basket Boat' or 'Basket Bike' - that's just to name a few!!!
TAR4: Masquerade Roadblock in Italy, 'Mozart' or 'Beethoven' Detour in Austria, the whole Amsterdam leg <333, Indian bull RB, epic rope climbing battle between Millie & Chuck and Kelly & Jon and best of all - 'Strong Stomach' or 'Strong Hands' in South Korea!!!
TAR5: Chocolate RB in San Carlos de Bariloche, caviar-eating, egg-eating, broken ox
TAR6: Mount Hua padlock RB, Corsican FF, Swedish haybales, Hungarian chilli eating
TAR7: The Meatblock in Mendoza, South African orphanage, everything in London and Jamaica
TAR8: Legs 1-4 were pretty full of great tasks!
TAR9: Thai Roadblock and Thai Detour for sure!!!
TAR10: La Tomatina Festival
TAR11: Krakow sausage eating, Krakow horse knocking over Charla <333, 'Cookie Confection' Detour, the Hong Kong 'Kung Fu Fighting'
TAR12: Where to start! Donkey leading in Ireland, camel milking, teaching kids, dancing, gold panning all in Burkina Faso, Lithuanian Detour, Italian Detour <333, Japanese 'Sense of Touch' and 'Sense of Smell' Detour + taxi driving RB and the best final leg in TAR history!
TAR13: Colourful India Roadblock, 'Teary Eyed' or 'Bleary Eyed' Detour, Fighting Cholitas RB in Bolivia, Kazakhstan cow costumes, New Zealand Maori warriors and kiwi squashing! Great memory task, too!
TAR14: Romanian 'Vampire Remains' plus 'Balancing Dolly' or 'Austrian Folly' in Leg 2 and the Swiss cheese in Leg 1
TAR15: Absolutely everything in Dubai, as well as more Swedish haybales
TAR16: Champagne towers and 'Ox Trot' in Seychelles
TAR17: 'Classical Music' or 'Classic Film' Detour in Russia and the Norwegian FF and the watermelon slingshot of course!!!
TAR18: Kunming dinosaur sculpture, tea-tasting RB in India, absolutely everything that took place within Europe and the Brazilian Detour
TAR19: Yuck... nothing comes to mind, except maybe some of the tasks on Leg 7 (Malawi)
TAR20: So far, everything in Paraguay