An efficient strategy to produce forests of aligned nanowires and nail-like micrometer-sized structures, whose density can be tuned in a broad range, is reported in this study. It relies on a combination of two template-assisted nanofabrication/patterning methods: electrochemical growth of metal nanowires in nanoporous sacrificial templates and partial masking of a surface with a self-assembled colloidal monolayer. A great potential of this novel approach, termed here colloidal occlusion template method, is demonstrated on the example of the fabrication of omniphobic surfaces comprised of nickel micronails whose density is varied to approach highest possible contact angles. After chemical modification to reduce their surface tension, these microstructures with reentrant geometry support the non-wetting Cassie state for both high-surface-tension water and low-surface-tension hexadecane. In particular, superhydrophobic behavior (contact angles exceeding 150 degrees) is found for water, while oleophobicity (contact angles approaching 110 degrees) is observed for hexadecane. The proposed approach can be exploited for the fabrication of a large variety of supported high-aspect-ratio nano/microstructures in applications where a surface density of features has to be several orders of magnitude lower than can be obtained with conventional template methods.