One Contador moment I'll never forget? The bloody chain gate and the reason is not that I was a Contador fan back then 
Another memory I'll never forget (for sad reasons to be honest) was his downhill attack with Kreuziger in the Alpe d'Huez stage 2013. I planned to go to an indoor climbing wall with a friend that day and had to leave while he was attacking and had a little gap. I was super excited, recorded the stage and then left looking forward to watching the rest of the stage that evening. Unfortunately I fractured my elbow when I fell of the wall that day and I spent the whole next day in hospital daydreaming about how the rest of the stage went and I imagined how he beat Froome. When I came home I was very excited watched the race and was incredibly disappointed to see that Froome basically won the tour that day despite losing time to Quintana and Purito.
The two final Paris Nice stages in 2016 and 2017 were both absolutely heartbreaking as well. I remember that in 2016 people already said that Contador can't lose the race anymore when he was in front of Thomas on top of the Eze an when the same happened in 2017, but with Henao and not Thomas and people were again already calling Contador the winner, I remember thinking "no not this again". I really saw that coming in that moment.
One of the most beautiful attacks from Contador I remember was him going berserk on stage 18 in the giro 2015. I watched that stage again around one week ago and I got incredibly nostalgic watching a giro 2015 stage again. That gt was so absolutely incredible. The fact that this stage doesn't immediately come to your mind when you talk about that giro just proves how many incredible moments that race had. Just to refresh your memory. Stage 18 was the one where Landa was caught up in a crash before the final climb of the day, which started with almost 50 kilometers to go. Contador had a huge lead and there was absolutely no need to attack there but since Astana attacked before the Mortirolo when he had a mechanical he took revenge and attacked as soon as the road went upwards. He ended up finishing the stage over one minute in front of all other gc contenders (except Hesjedal who had his typical world class climbing day out of nowhere)
Another stage, I didn't watch live, but saw many times on youtube is the stage to Loudenvielle in the 2007 tour de france. That was the stage when he attacked Rasmussen around 536 times on probably less than 5 kilometers. He was so freakin close to cracking Rasmussen there but just couldn't quite do it.
Talking about the tour 2007, I realized some time ago that my first ever memory of a cycling race comes from him in that tour. Basically I remember that I was watching a mtf where two guys dropped everyone else and I remember that one of these guys was called Rasmussen and that the guy called Rasmussen didn't win the stage. Therefore this can basically only the the Plateau de Beille stage from that tour which Contador won.
The queen stage of the giro 2011 maybe wasn't all about Contador but still he was the one who for absolutely no reason attacked on the third last climb and therefore started one of the most epic high mountain battles of modern cycling. And ofc he finished that stage by dropping all his rivals on the final climb (although Scarponi almost caught him). I'll probably mostly remember this stage for Nibali's incredible downhill rides and him blowing up on the Fedaia which were basically the main reason the pace always stayed that high for the last 50 km, but still Contador played a huge role in the narrative of that stage.
Many other great stages have already been mentioned. Fuente Dé was without a doubt his masterpiece, Alpe d'Huez 2011 was one of the best stages of this decade, the final stage of the Dauphine 2014 was heartbreaking but one of the best finales of a stage race I've ever seen, and I also loved how he crushed everyone on the climb at the beginning of the Pais Vasco TT 2016. I remember seeing these time splits and simply not believing them because Contador wasn't that dominant on the previous stages.
But actually I think one of my greatest memories of Contador will be the whole vuelta this year. How he attacked almost every day and was almost the only reason why this vuelta was entertaining is something I've never seen before and I'm not sure I'll ever see anything like that again.
Another memory I'll never forget (for sad reasons to be honest) was his downhill attack with Kreuziger in the Alpe d'Huez stage 2013. I planned to go to an indoor climbing wall with a friend that day and had to leave while he was attacking and had a little gap. I was super excited, recorded the stage and then left looking forward to watching the rest of the stage that evening. Unfortunately I fractured my elbow when I fell of the wall that day and I spent the whole next day in hospital daydreaming about how the rest of the stage went and I imagined how he beat Froome. When I came home I was very excited watched the race and was incredibly disappointed to see that Froome basically won the tour that day despite losing time to Quintana and Purito.
The two final Paris Nice stages in 2016 and 2017 were both absolutely heartbreaking as well. I remember that in 2016 people already said that Contador can't lose the race anymore when he was in front of Thomas on top of the Eze an when the same happened in 2017, but with Henao and not Thomas and people were again already calling Contador the winner, I remember thinking "no not this again". I really saw that coming in that moment.
One of the most beautiful attacks from Contador I remember was him going berserk on stage 18 in the giro 2015. I watched that stage again around one week ago and I got incredibly nostalgic watching a giro 2015 stage again. That gt was so absolutely incredible. The fact that this stage doesn't immediately come to your mind when you talk about that giro just proves how many incredible moments that race had. Just to refresh your memory. Stage 18 was the one where Landa was caught up in a crash before the final climb of the day, which started with almost 50 kilometers to go. Contador had a huge lead and there was absolutely no need to attack there but since Astana attacked before the Mortirolo when he had a mechanical he took revenge and attacked as soon as the road went upwards. He ended up finishing the stage over one minute in front of all other gc contenders (except Hesjedal who had his typical world class climbing day out of nowhere)
Another stage, I didn't watch live, but saw many times on youtube is the stage to Loudenvielle in the 2007 tour de france. That was the stage when he attacked Rasmussen around 536 times on probably less than 5 kilometers. He was so freakin close to cracking Rasmussen there but just couldn't quite do it.
Talking about the tour 2007, I realized some time ago that my first ever memory of a cycling race comes from him in that tour. Basically I remember that I was watching a mtf where two guys dropped everyone else and I remember that one of these guys was called Rasmussen and that the guy called Rasmussen didn't win the stage. Therefore this can basically only the the Plateau de Beille stage from that tour which Contador won.
The queen stage of the giro 2011 maybe wasn't all about Contador but still he was the one who for absolutely no reason attacked on the third last climb and therefore started one of the most epic high mountain battles of modern cycling. And ofc he finished that stage by dropping all his rivals on the final climb (although Scarponi almost caught him). I'll probably mostly remember this stage for Nibali's incredible downhill rides and him blowing up on the Fedaia which were basically the main reason the pace always stayed that high for the last 50 km, but still Contador played a huge role in the narrative of that stage.
Many other great stages have already been mentioned. Fuente Dé was without a doubt his masterpiece, Alpe d'Huez 2011 was one of the best stages of this decade, the final stage of the Dauphine 2014 was heartbreaking but one of the best finales of a stage race I've ever seen, and I also loved how he crushed everyone on the climb at the beginning of the Pais Vasco TT 2016. I remember seeing these time splits and simply not believing them because Contador wasn't that dominant on the previous stages.
But actually I think one of my greatest memories of Contador will be the whole vuelta this year. How he attacked almost every day and was almost the only reason why this vuelta was entertaining is something I've never seen before and I'm not sure I'll ever see anything like that again.