Weightlifting is a wide category. While this is a list of feats of strength it really wouldn’t be complete without a mention of this area. Any standard exercises taken to an extreme can be a feat of strength. After all, what is a feat of strength but a demonstration of strength.
I’d say that any exercise done with more weight than almost anyone could handle will qualify. Whether you are doing a jerk, squat, situp (shown below of Bud Jeffries), curl, press or anything else.
Don’t think that you have to go off the normal path to do feats of strength. Although some would say that doing even regular exercises with these kinds of weight are of the ‘normal path’.
Here is Paul Anderson pressing a 300 lb. dumbbell (and making it look easy).