Chinese star Ding Junhui became the seventh seed to crash out of the World Championship after losing a final-frame decider against Welshman Ryan Day.
Ding, the world number 10, won five frames in a row from 6-4 down to put himself one away from victory.
But Day, a former top-eight player who has dropped to 35 in the rankings, won the next three to force a decider.
Ding was poised for victory until he missed a red with the rest on 48, and Day pounced with a 64 break to win it.
The 32-year-old will face another Chinese player, Mark Allen's conqueror Cao Yupeng, in the second round starting on Friday.
Last year's beaten finalist Judd Trump overcame stubborn resistance from another Welshman, Dominic Dale, before winning 10-7 to progress to a likely second-round meeting with Ali Carter, who leads Mark Davis 8-1.
Resuming 5-4 up after a first session on Tuesday in which he had been suffering the effects of food poisoning, the 22-year-old left-hander lost the opening two frames to fall 6-5 behind before finding his form with a break of 114 to level again.
But Dale, a two-time ranking event winner, hit back with an 80 to edge ahead 7-6 at the mid-session interval.
Trump responded with runs of 51 and 40 to draw level again before a brave top-spin cut on a red into the bottom corner, freeing up the rest of the pack, saw him regain the lead.
The first sign of Trump's trademark power potting re-emerged in the 16th frame, but he was also aided by a timely fluke when he missed a red to one corner only to knock a different one into the other corner.
At 9-7 down, Dale blew a great chance to extend the match further when he potted the final red only to fall out of position on the green, banging his fist on the table in frustration. Trump, despite rarely finding his best form, duly went on to seal victory.
Graeme Dott suffered his heaviest World Championship defeat as Joe Perry completed a 10-1 demolition of the Scot with the minimum of resistance.
Resuming 8-1 down after a nightmare first session, the 2006 world champion's woes continued as Perry took only 25 minutes to collect the two frames he required.
Breaks of 59 and 56 were enough for the Cambridge-based cueman to book a second-round date with Stephen Maguire starting on Thursday.
Dott, who admitted he would have given up entirely were it not for the prospect of being fined by World Snooker, only potted 86 balls in the match.
"If there was ever a nightmare in snooker, that was it," he said. "I played terrible. I don't think I've played worse, not only at the Crucible but as a professional. I just couldn't pot a ball. To play as bad as that is hard to understand, it's demoralising."
At 8-0 down Dott was facing the prospect of joining the late Eddie Charlton as the only player to be whitewashed (10-0 against John Parrott in 1992) in Crucible history, but he rallied to take the final frame of the first session.
"I couldn't have cared less if it was a whitewash, what difference would it make? Ten-nil or 10-1, it's still a drubbing.
"I just wanted out. I couldn't pot a ball, I couldn't hit the white. If you told me to hit the white in the last frame I'd have probably missed it. I just couldn't do anything.
"And it was actually more demoralising that Joe was playing so bad. he's beaten me 10-1 there and he's played rubbish. Joe's not played well at all there."
Perry, who only made four breaks over 50 himself, the highest a 59, said it was the worst he had ever seen Dott play.
"I wasn't happy with my own game, and was just trying not to feel sorry for my opponent," said the 2008 Crucible semi-finalist. "As a professional sportsman you can't do that but it was tough. I wouldn't have particularly wanted to whitewash Graeme."