Common Tiger Beetle - Carabidae: Cicindelinae: genus Cicindela (Iowa, USA). These aptly-named predatory beetles are renowned for their speed - one species has been clocked sprinting at 125 body-lengths per second, or about 9 kilometers per hour. They move so quickly, they can temporarily go blind!
One of the most remarkable longhorn beetles I've ever seen: Aristobia horridula, hitching a ride on the ferry from mainland Thailiand to Koh Chang island in 2012. The pom-pom-like extensions on the antennae maximize surface area for chemoreceptors, allowing the beetle to detect tiny amounts of pheromone from conspecifics.
A cute little leaf beetle trundles through the undergrowth in Monverde, Costa Rica. (Chrysomelidae, subfamily Eumolpinae, possibly Brachypnoea)
