The cop (forget his name) that responded to the baseball card call is the same cop who responded to Skyler's call about Walt's "breaking and entering".
Stacy (Kaylee's mom) also needs to be added to the list. She appeared briefly in one scene on Breaking Bad, though she was played by a different actress. Still, I think it counts.
You could consider Nacho as another. Yes, he didn't appear in person in Breaking Bad but his name was dropped in Season 2 of Breaking Bad and was confirmed by Gilligan, Gould and Mando to be the same Nacho.
The Mexican doctor (forget his name) who met with Mike this season is the same doctor from Season 4 of BB who performed surgery on Mike and Gus after Eladio's death.
One of the nurses from BB (again, can't remember the name) was in one of the hospitals in BCS.
"Gun Guy" from BB is on BCS for at least two episodes when Mike was purchasing a sniper rifle from him.
I think Nacho was briefly in the BB episode where Combo gets shot. He was in a black car and told Combo not to slang in their turf prior to him being killed, Combo then flashed a pistol in his waistband, IIRC.
Yeah, it was just two no-name dealers that worked for Gus.
Gilligan and Gould confirmed that Nacho never physically appeared on Breaking Bad--only mentioned in Season 2.
What becomes of Nacho is anyone's guess but Michael Mando suggested that "death isn't the only option for Nacho's ending" so let's hope they give him a good sendoff, whatever it ends up being.
At the rate they're going, they will have reintroduced every BB character in existence which is fine by me...except for Skyler, Flynn and Marie. Keep them the HELL away from this show--especially Skyler. What an insufferable....OK, I need to stop writing about Skyler, LOL!