Visible crew/equipment: After Indy and Henry have escaped from Castle Brunwald, Indy jumps into one of the boats, pulls the motor starter cord and jumps back out, then just as he bends over to release the boat from the piling, right between Indy's legs the black covered arm of a hidden crewmember appears from under the tarp taking hold of the throttle, steering the boat away from the pier. (01:02:40)
Visible crew/equipment: Right as Young Biff starts to chase after Marty through the tunnel, there is a shot of the wheel spinning around, and you can see the camera crew reflected in the hubcap. (01:29:45)
Visible crew/equipment: During Bud and Coffey's fight in the lab, we see a lightbulb swinging from side to side between the two men. If you look closely, you can see a hand (belonging to a third person) pushing the lightbulb. The only people in the room are Bud and Coffey. (01:44:16)
Visible crew/equipment: After Bond received a lighter from Felix and Della, he uses it, and the flame is big. In the beginning and the end, you can see a tube is connected to the lighter, and the tube goes into his suit. (00:15:00)
Visible crew/equipment: When the chairs are flying through the air in the courtroom, if you look closely, you can see the string pulling one of them. (00:34:30)
Visible crew/equipment: When Bernie walks out from his office bathroom and starts talking to Richard and Larry about the insurance policies, a boom mic reflection can be seen behind him - in the mirror's upper left corner. (00:13:05)
Visible crew/equipment: When the neighbours visit the Szalinskis to get their baseball and Nick opens the door, you can see the reflection of the cameras and lights in the glass.
Suggested correction: This would need more clarification. I couldn't see any string in the mentioned sequences - and for the record, I don't think strings were used, you can easily find interviews with the production team that mention the different trick at work here (they quite literally 'shot' the chairs up in the air).
Sammo ★