Plasmonic materials fabricated from precisely controlled metal nanostructures provide promising platforms for developing high-sensitivity sensing devices, such as pH sensors, organic vapor sensors, and other chemical sensors. Over the past several decades, a number of unconventional methods for preparing localized surface plasmon resonance (LSPR)-based metal nanostructures have been developed in an effort to design high-fidelity sensors. Recent advances in plasmon-based optical sensors based on plasmonic nanostructures have made remarkable progress in overcoming the constraints of conventional optical sensors in terms of providing tunability, improved sensitivity, and good fidelity. In this review, we highlight the current state of the art in this field with an emphasis on the fabrication of plasmonic materials using unconventional methods and their demonstrated applications. We describe the remarkable achievements that have improved the performance of sensors for certain sensing systems. Finally, we present a perspective on the future development of LSPR sensors, including a discussion of the advances needed to elevate sensor performance to a level required for practical devices in the laboratory and in medical diagnostics.