There are always players who are on the bench who have won NBA championships. Not every player gets to play in the NBA Finals depending on the matchup, the skill of the opposition and how much experience the player has. They are still a part of the team, but do not get the playing time like some of the other players do. That being said, some players are much worse than others.
Some of the worst Larry O'Brien trophy winners were not expected to be on this list after being highly regarded draft picks. College superstar Adam Morrison from Gonzaga and former second overall pick Darko Milicic won titles with the Lakers and Pistons respectively despite offering very little production to the victorious team.
In some situations, a player may have had a legitimate career at one point, but by the time they won a championship they were more of a glorified cheerleader. Spurs guard Jacque Vaughn and big man Melvin Ely are two players who were utilized in this role.
Many international players that get drafted never come over to play in the NBA. Some of the players who do end up having fantastic careers but many others do not. Son Yue played sparingly in his first NBA season but was eventually recalled for the 2009 Playoffs, in which he averaged zero minutes per game for the LA Lakers. He won a championship without gaining a single statistic.
Another Laker, Stanislav Medvedenko, was so bad in the eyes of star player Kobe Bryant that Kobe felt the need to say, "There's one teammate that was just so bad. He was so bad". However, the big man would won two championship rings and even had a season where he scraped together eight points per game later in his career.