During Better Call Saul's “Bagman,” Jimmy (Bob Odenkirk) gets stuck in the middle of a shootout between the cartel and Mike Ehrmantraut (Jonathan Banks), resulting in the destruction of his beloved “World’s 2nd Best Lawyer” travel mug. When Jimmy notices that a bullet hole went clean through the mug, Jimmy becomes very emotional over its destruction, but why does the "World's 2nd Best Lawyer" mug mean so much to Jimmy?
In Better Call Saul season 5, episode 8, “Bagman,” Jimmy volunteers to pick up Lalo Salamanca’s (Tony Dalton) bail money in a remote location close to the Mexican border. Meeting The Cousins out in the desert, everything goes smoothly during the handoff of the money, but things quickly go astray when Jimmy begins his journey back home. Followed by an unknown vehicle, Jimmy is forced to pull over when he’s cornered by armed cartel members. As Jimmy steps out of his car, the cartel steals the $7 million for Lalo’s bail and are about to kill Jimmy when Mike saves him at the last second by shooting the cartel members from a distance. During the shootout, not only does Mike take out all of the cartel members except one, but he destroys two distinctive artifacts belonging to Jimmy that have been present since the early seasons of Better Call Saul: his 1998 Suzuki Esteem and his “World’s 2nd Best Lawyer” mug.
The “World’s 2nd Best Lawyer” mug has been with Jimmy since the second episode of season 2, “Cobbler.” The mug was a gift from Kim Wexler (Rhea Seehorn), Jimmy’s former law partner and current wife, to congratulate him for being hired as a partner at the Davis & Main law firm. While the mug originally read “World’s Best Lawyer,” Kim added on the “2nd” as a joke since she was a lawyer employed at Chuck McGill’s (Michael McKean) law firm, Hamlin, Hamlin & McGill. After attaining his first real job as a big-shot lawyer working the substantial Sandpiper lawsuit at Davis & Main, the mug came to represent Jimmy’s accomplishment of becoming a straight-laced lawyer like his brother Chuck, putting his sordid past, in which he ran schemes under the con-artist alias “Slippin’ Jimmy,” behind him.
In the same episode, however, the mug doesn't fit within the cup holder of Jimmy’s new company-issued Mercedes-Benz, but fits perfectly within his run-down Suzuki Esteem. The symbolism makes it pretty clear that Jimmy doesn’t fit in at Davis & Main and by extension, doesn’t fit the role of an upstanding corporate lawyer, which is eventually proven when Jimmy gets fired from Davis & Main during season 2. Since the mug represents the part of Jimmy striving to be a better, more respectable lawyer, it is also Jimmy’s last remaining connection to his brother Chuck, who died at the end of season 3. When Jimmy first set out to become a lawyer, it was in part due to his admiration for his brother, but Chuck never really believed Jimmy could outgrow his "Slippin' Jimmy" antics and thought he would besmirch the sanctity of the law with his unorthodox methods.
With this in mind, the mug exemplified Jimmy’s constant struggle between practicing moral integrity as the lawyer Jimmy McGill and reverting to his baser “Slippin’ Jimmy” instincts, using tricks and schemes to win a case. When his mug was destroyed in the episode “Bagman,” it was the moment when the struggle was finally over, marking the end of Jimmy McGill as an ethical lawyer and completing his descent into the criminal lawyer Saul Goodman. The two episodes "Cobbler" and "Bagman," which detail the introduction and end of Jimmy's favorite mug, nicely bookended Jimmy's journey from McGill to Goodman, since the former marked his finest moment as a lawyer, being hired by a prestigious law firm, while the latter exhibited his lowest point, in which he befriended the cartel and picked up illegally obtained cash for an immoral client.
While the destruction of Jimmy’s favorite travel mug in Better Call Saul appears to be a tough loss for Jimmy, it does explain why Saul Goodman can ironically be seen drinking from the upgraded “World’s Greatest Lawyer” mug in Breaking Bad.