My 2 cents:
Leg 1: Season 7 - Long Beach to Cuzco, PeruDebbie and Bianca winning the leg
Amazing scenery of the Andes. Decent detour, llama or rope basket.
Runner-up: Season 5 - Santa Monica to Punta del Este, Uruguay...Charla and Evil Myrna carrying that 50lb slab of beef + both Kami/Karli and Chip/Kim missing the clue box across the hotel and having to track back, incredible suspense.
Leg 2: Season 1 - Songwe Village to ParisThe safari detour, the roadblock on top of the Eiffel Tower (I love those old-school tasks, they were no gimmes, not everything was handed to them on a platter like nowadays), Lenny not spotting the flag on the Arc of Triumph then lying about it to his partner, Karyn subsequently tearing him a new one (the first ever emotional meltdown in TAR history?).
Runner-up: Season 10 - Beijing to Mongolia...one of the most exotic locations ever + ox running wild!
Leg 3: Season 3 - Cancún to Stonehaven, ScotlandKen and Gerard (one of my all-time favorite teams) making a hash of it on the punting detour in Cambridge but taking it all in good humour, the English crowd good-heartedly cheering them on, Cambridgeshire, the highlands games roadblock at the end. Great episode.
Runner-up: Season 12 - Amsterdam to Ouagadougou, Burkina Faso...I loved the detour in that village school (Teach It or Learn It) + the camel milking roadblock.
On a side note, I hate third legs, that's usually when my favorite teams out of the gate get eliminated LOL Lena and Kristy in that dishearteningly unlucky hay roadblock, Debbie and Bianca boneheadedly driving more than 2 hours on the wrong Chilean highway (still can't believe they messed up so bad, they looked one of the strongest all-female teams up until then) etc.
Leg 4: Season 11 - Puerto Montt, Chile to Ushuaia, ArgentinaOne reason and one only: Rob and Amber getting eliminated
I waited a long time for that. Granted, they were undone by the mail sorting roadblock where it was all luck but very satisfying still. All the sweeter since it was Rob who did the roadblock; sure, it was luck like I said, but they were eliminated because of HIM (you knew that fool would have said some cocky crap had it been Amber's detour, like HE didn't get really eliminated or something stupid like that blah blah blah).
Runner-up: Season 10 - Hanoi to Ha Long Bay, Vietnam...Brilliant scenery of Ha Long Bay + a very tough detour, teams had to row in very windy conditions.
Leg 5: Season 16 - Hamburg to Wargemoulin-Hurlus, FranceNo roadblock and nothing much happening in the detour (they only had to crawl, which is pretty lame) or race-wise, but I have to give the producers major props for staging that WWI battlefield. You know a lot of planning went into that. So a shout out to production more than anything else.
Runner-up: Season 9 - Catania to Siracuse...Monica (for my money, the second-hottest TAR babe ever, after the incomparable Dustin
) with all that fish juice down her tank top, I mean, that's hard to beat, right? hahaha
Leg 6: Season 4 - Amsterdam to MumbaiA leg in India has to make the list, just has to. The boob-grabbin' and a*s-pinchin' on the Indian trains, a little peek of Bollywood, Tian's Wonder Woman effort carrying those 20 Palai fish (hot chick + fish juice, a theme is developing here...). Tian was an awesome competitor, too bad she was stuck with the fairly useless Jaree.
Runner-up: Season 5 - Giza to Luxor...The extraordinary scenery of Egypt + a tough roadblock digging for the scarab ("What is a scarab? A rock?").
Leg 7: Season 12 - Dubrovnik to FlorenceBased largely on the cool challenges. Roadblock: spotting "VINCI" from the air. Detour: the Leonardo crane, which was hard, and the local flag routine, which wasn't all that hard but I loved the pageantry.
Runner-up: Season 16 - Champagne-Ardenne to the Seychelles...for the reasons Woden pointed out in the original post.
Leg 8: Season 10 - Mauritius to Antananarivo, MadagascarMy baby Dustin and Kandice working well with the Cho Bros, then beating the FF teams to the Pit Stop. I can't think of another time that has happened before or since.
Runner-up, tie: Season 6 - Corsica to Lalibela, Ethiopia (for the location, mainly, it will be a long, loooong time TAR will be back to that part of the world again, if ever) and Season 3 - Füssen to Grindelwald (for the detour Count the Money).
Leg 9: Season 2 - Sydney to Coober Pedy, South AustraliaOne of the greatest TAR lines ever, "I'm not a miner! No, you're an idiot" (Tara to Wil, of course). Blake and Paige (another all-time favorite) smokin' the golf detour in 130° heat. The boomerang roadblock.
Runner-up: Season 4 - Malaysia...Chip and Reichen going to the FF by mistake, Jon and Kelly missing on said FF and getting way behind, Chuck and Millie Mole getting desperately lost and allowing J & K back into it, Jon overtaking Chuck on that rattan ladder roadblock (they showed them side by side, which was very cool). Oh the suspense! (also helped that I was pulling for J & K that season).
Leg 10: Season 14 - Guilin to BeijingFull disclosure: I was rooting for Jaime and Cara that season. Cara smokin' the eating detour and, of course, Jennifer and her potty break literally costing them a spot in the Final 3 and a chance at the million dollars. Even if my favorites weren't saved by that awful moment of madness, you have to admit it was one of the most memorable TAR moments ever - a potential $1m potty break
Runner-up: Season 4 - Malaysia to Seoul...TAR in the DMZ, a few miles from North Korea, freakin' North Korea, AMAZING Race is right!!! Jon and Kelly winning the leg thanks largely to Kelly breaking those boards at the Tae Kwon Do detour (and almost breaking her hand in the process). The 2 most physically capable of the remaining 4 teams (Chip/Reichen and Jeff/David not choosing the TKD detour, opting to eat the live octopuses instead, which was a huge head scratcher).
Leg 11: Season 3 - Singapore to HCMC, VietnamOne of the most baffling moments ever for me, Derek and Drew's moment of madness, missing that clue box in HCMC. They were smart racers, I still can't understand why they didn't just follow the yellow flags from one end (the ferry) all the way back to the other, where the clue box was. They must have just panicked. I wasn't pulling for them (I was pulling for Ken and Gerard that season) but I still felt bad for D & D, they dominated that season and "deserved" to win it more than any other team. One brain cramp and poof, gone.
Runner-up: Season 6 - Shanghai to Xi'an...All 4 girls remaining doing the roadblock + Xi'an and the Terra Cotta Warriors (near the top of my to-visit list, hopefully next spring).
Leg 12/13, Finishing leg: Season 7 - Jamaica to MiamiRey de los Habanos, baby!!!! Rob and Amber didn't win, neh neh neh! Very mature, I know, who cares, neh neh neh, Romber didn't win!!! Can't explain how satisfying that was for me.
Runner-up: Season 2 - Maui to Sausalito...Agree that in term of suspense, it was the best, by far. I don't rank it at the very top because a) I couldn't stand Alex and his stupid South Boston accent b) I really don't think that finish was very fair at all. Have teams run like a hundred yards to the finish mat is okay, but that finishing run was a very, very, VERY long one, any all-male team would have won over either a couple or an all-female team, provided their taxis weren't too far behind. And that's exactly what happened. Chris and Alex had a huge advantage there, more so than in any other final leg before or since, poor design from the producers, on the most important leg, IMO.