No specific order.
F1 at Interlagos, no need to explain I suppose.
F1 at Barcelona for the Williams win. Wasn't sure I'd ever see that again at some point.
F1 at Monaco. 6 cars train fighting for the win under the drizzle. A bit 1992-esque, all proportions kept. Plus Mark pulling off a second win here was quite nice to see.
GP2 at Valencia, sprint:
video. See F1, no need for stupid DRS for exciting racing. Quite a nice pass by Razia BTW, the guy gets awful press for some reason, but this was a good ride.
GP3 at Silverstone, race 2: Will Buller going from 28th to 1st in a wet/damp race.
GP3 at Monza, race 1 and 2. 4 drivers for the title. The top 3 - Evans, Da Costa, Vainio - all hitting trouble early. Daniel Abt almost doing the unthinkable come-back, only to get pipped by Mitch Evans in the last lap of the last race. A mix of the 2007 and 2008 F1WC finales, if you wish.
F3.5 at Barcelona, race 2: Robin Frijns taking a superb rookie title, even though the incident with Bianchi was quite a bummer really.
F3 at Macau: Just like Indy, Macau is Macau, and all races are special here. Not a very eventful race that one, but Da Costa winning in a 3rd different category in one single calendar year was just shockingly impressive for today's modern era. Shame for the support races tragedies, though.
WTCC at Monza: Drafting always makes for good racing here. Yvan Muller doing another of his
miraculous saves on his way to the race 2 win. Tarquini's surprise pole on his ageing Seat was nice too.
Indy 500. Should be on top really. What a ride.
Finish with Japanese commentary. I really wanted a new winner badly, but oh well, congrats to Dario. Gutted that TK didn't pull it off anyway. He sure got the
public support, though. When he's gonna win, he's gonna tear that place down for sure...
IndyCar: hard to pin down a specific race apart from the 500, but bar Lotus and the off-track controversies, this season was great. I'll pick Iowa anyway. Maybe Edmonton too, was cool to see Tag up front, and it was the first caution-free race in quite a while.
MotoGP at Philip Island: Not an eventful race, but the win of a wounded Stoner, at home, for his penultimate GP ever, was very, very special.
Moto2 at Sepang: A crazy race in appaling conditions. A local wildcard no one had heard of outside Malaysia coming from around 20-30th to take the lead, then finish 4th in the end. Nice 3 way battle up front in the last few laps, but the red flag finish was a shame.
Without picking a race in particular, the growing
Moto2 rivalry between Marc Marquez and Pol Espargaro was very, very entertaining. Little Pol really made a first name for himself this year, especially with his banzai last lap attack at Estoril. You also had some great hardchargers on their wings, especially Andrea Iannone and Scott Redding, two entertaining personalities and very fiery racers on the track.
Moto3. Hard to pick a race here, too. Very good year for the new class. Indy was great... Last lap dash between Vinales, Cortese and Salom. Maverick binning it - a big turning point at the championship - and the under-rated Luis Salom taking his first ever win. Also, Jonas Folger taking his first podium at his first race post-Ioda purgatory.
NASCAR: some good stuff among the few races I've watched. Michigan in Trucks - I actually do enjoy Trucks more, because the races are much shorter, which means less trying-to-luck-into-the-front-with-lucky-strategy, and more pedal-to-the-metal racing. Also, there seems to be less fake cautions. Plus, there's none of the tired NASCAR Cup-hype machine, and fewer Cup ringers blatently ruining the fun than you have in NNS. Talladega #2 in Cup was good too - yes, the final lap pile-up was quite ugly and unfortunate... But wow, good job everyone for staying out of trouble for so long! Say whatever you want about pack racing, but having a pack of 30+ cabs running millimeters to each other at 190+ mph for 3 hours is quite breathtaking.
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At last but not least:
F3 Open at Barcelona, race 2.
Just to put things into perspective: it was the season finale, and Niccolo Schiro and Giancarlo Raimondo were head-to-head for the title. After a very eventful dry/wet/dry race in which both Schiro and Raimondo looked to be done at some point(won't go into details), Raimondo appears to be in position to win the title, but at 2 minutes to go, he dives into the pits for no apparent reason, stops a few seconds at his box, then he is told by his very calm crew to go out... Every single observer must have thought, seriously, what has just happened there, why would you throw away a title like that, and why did the crew look so unconcerned...? Then Raimondo, who probably must have had serious mechanical problems, has to stop in the middle of the track at the final corner. The top runners avoid him... But his title rival Schiro hits him in the final lap, and limps to the line on 3 wheels to claim the title.
Just when you thought you'd seen it all, really... BTW, Schiro and Raimondo were team-mates, which certainly made for interresting conversations in the post-race debrief.
Highlights
here(doesn't do such a good job at capturing the sheer unpredictability and drama of the race, sadly)
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Also, as a bonus, the worst races:
NNS at Montreal: a true farce. That day I lost a lot of respect for NASCAR and JV. I for one won't cry over the loss of Montreal on the calendar, it's better for everyone's mental health and tempers really. Mid-Ohio should provide some better racing at least.
GP3 at Hockenheim: over the course of the 2 races there were more SC laps than green flag laps, and I am not joking. Was quite disturbing to see Machado and Piria sent to the hospital after freak crashes, but at least it was serious for none of them. Great battle for the lead between Niederhauser and Daly in race 1 anyway, and a nice, important win for Evans in race 2.
BTCC at Brands and Donington: quite a crash fest really. Lost a lot of respect for Mr Plato. Donington race 3 decided after 2, different and unrelated post-race investigations, never good to see. At least there was Tony Gilham's 3rd place in his green and pink Civic for consolation...
Honorable mention to that for me (even though I wasn't there) link added to OP and here. 
