Not only did the Brazil midfielder set up a 2-0 win for the defending champions at the Stadium of Light, but, as a former Newcastle player, he made the most of his moment, sending a message to the home supporters by cupping his ears as he ran towards the corner in celebration.
Guimaraes joined the Gunners from Sunderland's fierce northeast rivals in the summer so will have been well aware of the significance of his goal. Coming on as a halftime substitute, he curled a long-range shot into the top corner in the 58th minute.
The goal came two minutes after Arsenal's David Raya saved Enzo Le Fee's penalty.
"It is a beautiful moment for me and my family," Guimaraes told TNT Sports.
"Everyone knows my amazing history at Newcastle, but now I'm trying to create a new history here. I've started on the right foot."
Bukayo Saka sealed the win with a penalty in the seventh minute of added time after Reinildo Mandava was sent off for bringing down the forward in the box.
Manchester City are three points behind Arsenal in second place and play Manchester United on Sunday.
Earlier on Saturday (Sunday AEST), Australian Lucas Herrington enjoyed another big day in his Premier League education as his Hull City side eked out a 2-2 draw at Chelsea to maintain their four-game unbeaten league start.
Chelsea weren't the only big side to drop points at home as Liverpool and struggling Tottenham were also held to draws, while Aston Villa lost again.
The Blues' fragile defence was exposed again by newly-promoted Hull at Stamford Bridge, with 19-year-old Herrington again playing his part with a half-hour off the bench.
The young Socceroo keeps impressing at the back but it's Chelsea's defensive problems that are becoming eye-catching.
Xabi Alonso's team have conceded at least two goals in each of their league games and 12 goals in six matches in all competitions.
"We can do better. We got what we deserved," Alonso said.
"We need to be more solid and be more controlled."
It took a goal from Joao Pedro in the 66th to salvage a draw after Mohamed Belloumi's double had seen the Tigers, who now have eight points from four matches, rally from 1-0 down to lead 2-1. Morgan Rogers had put the hosts ahead in the seventh minute.
Liverpool have spent a fortune rebuilding their attack over the past two seasons, but they were held to a 0-0 draw a Fulham team who hadn't kept a clean sheet and were pointless going into the game.
"When you draw, especially at home, you can't be happy," new boss Andoni Iraola said.
"Today we lacked a bit of freshness and we did not do enough offensively to make the difference."
Tottenham remain goalless and winless after a summer of heavy spending and the boos rang out after their goalless draw at home to Everton as they voiced their disapproval at it being more than six hours since Spurs last scored.
Villa's nightmare start to the season also continued with a 2-1 loss at home to Nottingham Forest, while Ipswich beat Crystal Palace 3-2 and Bournemouth drew 2-2 with Brentford.
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