H₂, molecular hydrogen (2 Hydrogen atoms)

Halo 2

Hydrogen-2, H-2, ²H (a.k.a. Deuterium), an isotope of Hydrogen (1 proton, 1 neutron, 1 electron)

H-2 is the mouse equivalent of the Human Leukocyte Antigen

In the U.S., a visa (document) issued for temporary non-agricultural employment

The SH-2 Seasprite, a U.S. helicopter

H2 (manga)

H₂ histamine receptor

British NVC community H2, Calluna vulgaris - Ulex minor heath

H2 (DBMS) Database Engine, an open source Java SQL DBMS

the IATA code for Sky Airline

a model name for a Hummer, see H2 (Hummer)

Harrison Number Two, an 18th century marine chronometer designed by John Harrison

Hollywood Squares, referred to as H² informally during the final two seasons (2002-2004) seasons of the Tom Bergeron version.

Interstate H-2 is an intrastate interstate highway located on the island of Oahu in Hawaii

a H II region, a cloud in which star formation takes place

Lake Havasu City Airport, with the IATA airport code HII

H-II, H-IIA and H-IIB, families of liquid-fuelled rockets

the H-II Transfer Vehicle, a JAXA unmanned spacecraft

The H2 SUV/SUT/Hydrogen is the second vehicle sold under the Hummer marque of General Motors