Liverpool host Manchester United on Sunday in the 186th installment of a bitter rivalry that has brought out the worst in some of the sport's biggest stars. Here we look at five of the most notorious flashpoints in England's premier grudge match:
Teargas horror stuns United
In the 1980s English football was being torn apart by the hooligan gangs that regularly ran riot on the terraces and United's visit to Anfield in February 1986 provoked an especially sinister incident.
As United manager Ron Atkinson and his players climbed off their team coach outside Liverpool's stadium and headed towards the dressing rooms they were stunned by a fan wielding a can of teargas.
"We got off the coach and all of a sudden something hit us," Atkinson recalled. "I thought it was fumes off new paint or something, but it was teargas."
United midfielder Clayton Blackmore was so overcome he could not play and the subsequent 1-1 draw was played out in a suitably poisonous atmosphere.
Child's play turns nasty as Dalglish slams Fergie
Over two years into his reign at United, Alex Ferguson was struggling to knock Liverpool from their perch on top of English football and the Scot's frustration boiled over after 3-3 draw at Anfield in April 1988, prompting a scathing response from then Reds boss Kenny Dalglish.
Ferguson, incensed by the dismissal of United's Colin Gibson, hinted that referees were biased towards Liverpool when he told radio reporters that it was no surprise managers "have to leave here choking on their own vomit, biting their tongue, afraid to tell the truth".
But Dalglish wasn't daunted by Ferguson's rant and, carrying his baby daughter Lauren past the United manager, he turned and said: "You'll get more sense out of her."
Benitez loses the plot in 'facts' rant
For the first time in years, Liverpool were firmly in the title race in January 2009 and had United in their sights ... until Reds boss Rafael Benitez launched a remarkable verbal blast at Ferguson.
Benitez appeared to be cracking under the pressure of battling with Ferguson, a clever manipulator of the media, as he used a press conference to attack the United chief with a series of alleged 'facts' about his counterpart's treatment of officials.
Benitez claimed Ferguson was "the only manager who will not be punished" for verbally attacking referees.
"We had a Respect campaign meeting and I said forget it, because Mr Ferguson is killing the referees," Benitez said.
The rant backfired spectacularly as Liverpool lost ground in the title race after Benitez's criticisms and it was United who finished as champions again.
Ambulance attack caps ugly Cup clash
When Liverpool defeated United 1-0 in an FA Cup fifth round tie in February 2006 it was their first win over the old enemy in five attempts, but the mood at Anfield was anything but celebratory.
One of the most vile encounters in the long history of their rivalry featured Liverpool fans tipping cups of urine onto United supporters in the seats below them, while coins were thrown at players by both sets of fans, who also chanted sick taunts about the Hillsborough and Munich tragedies.
The nadir was reached when United's Alan Smith suffered a broken leg. As Smith was taken to hospital in an ambulance, thugs attacked the vehicle on the streets outside Anfield and an attempt was made to turn it over.
Suarez disgraced after racial slur at Evra
Liverpool striker Luis Suarez was handed an eight-match ban and fined £40,000 for racially abusing United defender Patrice Evra during the October 2011 clash at Anfield.
Suarez was found to have called Evra a "negro" seven times in the course of the 1-1 draw and was described as "unreliable" and "inconsistent" when he gave evidence to the Football Association's disciplinary hearing.
When the two teams met again at Old Trafford in February this year, the festering feud between the players boiled over.
Uruguay's Suarez, feeling Evra had made too much of the situation, refused to acknowledge the Frenchman during the pre-match handshake and the United star responded by celebrating in front of his rival after his team's victory.