Please add: 1) an expression of surprise or bewilderment, concerning an event or accident. Disappointment or displeasure is clearly implied.
2) a signal of resignation, coming from the realization of one's powerlessness in a situation, or, alternatively, one's boredom.
1) You just unpacked a new camera to find the lens broken.
2) Your wife has just griped that your second attempt to clean out the garage is still inadequate. Here, wtf is preceded by "OK,....."