Recap / The X-Files S07 E06 "The Goldberg Variation"
AB Negative: Richie has a rare blood type, B-negative. And he's CMV negative. Cytomegalovirus, as Scully says.
Billy Needs an Organ: Richie has a hepatitis and he needs liver transplant. (Scully diagnosed him just by looking at him.) Alternatively, he could get in a special experimental treatment program in England. He's got a rare blood type and further complications.
Bullying The Dragon: What Weems thinks he's able to do against an angry mob boss, since Weems knows he's protected by dumb good luck.
Contrived Coincidence: One too many things have to fall into place for all these weird accidents to occur. Which is what Weems' good luck is all about.
Even when it looks like Scully accidentally breaks Weems' good luck streak, it turns out that was all part of the setup to get the mob boss killed... the one mob boss who's an organ donor and an exact match for Richie's transplant.