Let $X$ be a smooth, projective variety over $\mathbf{C}$ (to keep things simple) and let $\mathcal{F}$ be a vector bundle on $X$.
If $\mathcal{F}$ has a nowhere vanishing holomorphic section, then the top Chern class of $\mathcal{F}$ vanishes. Are there other (weaker), but "natural") conditions on $X$ and/or $\mathcal{F}$ which guarantee the vanishing of the top Chern class?