They Keep Killing Suzie - S1-E8
Visible crew/equipment: When Owen responds to Susie talking through the computer monitor and says "you frighten the s**t out of me" a boom mic drops into shot above his head.
End Of Days - S1-E13
Visible crew/equipment: After Lisa appears to Ianto in the holding area, she disappears, when the camera changes angles you can still see her standing in the corner of the room on the right side of the screen. (00:12:50)
Answer: Several times during the episode, most notably at the beginning when the old grave is discovered, Tosh holds a devise that looks a great deal like the Sonic Screwdriver that she uses to determine the age of the skeleton. However, a search of Google images shows that it is not the same thing.
OneHappyHusky