Cable cars. I know the cable is comprised of thousands of smaller metal cables and it's much stronger than it seems, but it's just one cable.
There's this marine park my family and I visit regularly, and to go from the lowland to the highland you either take the cable car (10 minutes), walk there (30 minutes) or leave the park and take a cab to the highland entrance (20 minutes). They take the cable car. I take the cab.
Towers like the Seattle Space Needle terrorize me. I can't go to the edge of the observation deck because I swear I can feel the tower leaning.
Ferris wheels. I'm afraid the damn wheel is going to roll onto the streets and wreak havoc on pedestrians and vehicles alike.
I've done Six Flags roller coasters and I have no issues with them because there is so much supporting structure visible and that reassures me. I know the attractions I mention are also designed to be perfectly safe but to me visually they seem like disasters waiting to happen.