As everyone here knows, it would be a stupid idea to switch from airplanes to cars out of safety/terrorism concerns: Cars are a much more risky means of transportation than airplanes. But what other major risks are there that many people systematically undervalue or are not even consciously aware of?
The same can be asked for chances.
In general: an unhealthy lifestyle. In the relevant context the overwhelming majority of people die of diseases when relatively old (and not accidents or violence).
Other than that: suicide is often underrated - it is often the main non-disease cause of death for males.
(Eg when checking the stats for my own demographic I had about a 6.55% risk of death the next 30 years. Out of this some 10% were from suicide, 5% from accidents and only 1.5% from infectious diseases but over 50% from malignant neoplasms and circulatory system diseases.)
Useful statistics: http://www.deathriskrankings.com/default.aspx?AspxAutoDetectCookieSupport=1 Some useful tips: http://longevity.about.com/od/liveto100/tp/Avoid-The-Top-Five-Killers-Of-Older-Men.htm