Geez, what a bunch of terrible answers. Elemental sulfur at normal temperature and pressure is a solid, and almost odorless. Elemental selenium and tellurium likewise are essentially odorless, although they form malodorous compounds. The question asks about elements.

Leaving aside as unknowable the odors of the short-lived transuranics that can only be created a few atoms at a time, the unquestionable champion is bromine, which gets its name from the Greek bromos, meaning stench. It’s both malodorous and powerfully irritating.

Another element named for its bad smell is osmium (from Greek osme, smell), but in this case it’s not the element itself but the compound it forms with oxygen, osmium tetroxide, that has the bad odor. However, elemental osmium exposed to air will soon generate enough OsO[math]_4[/math] to create a noticeable stink.