Of the non Brits Usain Bolt obviously but also the Georgian guy who won the 105+kg weightlifting. He was up against the defending champion a 27 stone Iranian. For those that don't know the competition is decided by combining the weights lifted in two lifts, the snatch (one movement) and clean and jerk (two movements) with three attempt allowed for each lift. In the snatch on his 3rd lift the Georgian lifted a WR 215kg, the Iranian then added a kilo for his 3rd lift and another WR. Then on to the clean and jerk.
With just the two aforementioned left in the competition the Iranian failed on his 3rd attempt at 257kg but actually got a unanimous clean lift from the judges correctly overruled a few minutes later by the video ref because he didn't lock his elbows first time. He was mightily peed off, went back out to remonstrate but with out success. The Georgian had failed twice at 257kg and went back on stage for the last lift of the competition and instead of complete silence the Iranians in the crowd started booing, he gestured to them, stuck another 1kg on the bar and lifted it whilst pulling faces at the Iranians for a new WR total of 473kg for the combined lifts. Just to put that into pounds and ounces he put 570lbs (40 stone) over his head!
For the Brits, so many outstanding performances to choose from but as a former international eights rower I'd have to go for the men's eight. It's the perfect team sport, each crew member goes way past their limits but can't give up for fear of letting down the other seven in the crew as each blade has to hit the water at exactly the same time and, if not pulled with maximum effort, would come out late. You go from peak fitness to not being able to climb out of the boat in just under 6 minutes.