4. K Eddie Murray: Sixth Round (pick No. 166), 1980
The Lions don't draft a kicker very often, but the couple times prior to the last time they did so it worked out very well. The first time was Murray in the sixth round of the 1980 draft. He only held the job for the next 12 seasons, and he's the second-leading scorer in Lions' history (1,113 points, behind Jason Hanson, the guy who replaced him). Murray also kicked in four playoff games for the Lions.
Murray became well-traveled as his career stretched through the 2000 season. A kicker rarely belongs on a list of draft steals, but in this case it fits.
3. CB Darius Slay: Second Round (Pick No. 36), 2013
Slay's tenure in Detroit ended abruptly in 2020 due to an ongoing conflict with Matt Patricia, when he was traded to the Philadephia Eagles. But that he fell to the 36th pick in the 2013 draft is easy to tab as a great steal (ESPN did so over the drafts from 2013-2022). Some good cornerbacks were taken before him, but none had an argument to be called the best cornerback in the league like Slay did for a time.
In 2017, Slay led the NFL with eight interceptions and 26 pass breakups on his way to earning his first Pro Bowl selection. He allowed just a 55.1 passer rating that year too, according to Pro Football Focus. He made the Pro Bowl in each of the next two years, and he's done so again in three straight years with the Eagles (2021-2023).
If you had a wide receiver in fantasy football who'd be going against him in a given week when he played for the Lions, you had to get ready for that receiver to deliver below expectations as he went for what was respectfully called a "Slay ride." His departure was the quintessential stupid move of the "Quinntricia" era, but Slay was an absolute draft steal for the Lions.