A teeny-tiny little carpet beetle (Anthrenus sp, Dermestidae, 2-3 mm) feeds on pollen in my yard in Iowa. Beetles from this family are reviled by entomologists the world over for their habit of infesting and damaging insect collections.
Brown Prionid, Orthosoma brunneum, from Iowa.
American carrion beetle, Necrophila americana (with bonus mites!) from Wisconsin. These beetles perform the unsightly but critical ecosystem service of consuming large dead mammals, breaking down their organic matter into smaller pieces so that it can be used by other organisms.