What weapon could the US have put into space?

The announcement by the United States that it has deployed a space weapon in Earth's orbit has raised questions about what weaponry is actually in space, and what role it could play in efforts by great powers to dominate that arena. Washington has given away little in its announcement. Secretary of the Air Force Troy Meink said the "on orbit" weapon was necessary to safeguard US forces against hostile enemy action, but gave no details about the weapon's capabilities or when it was put into orbit. So what could this weapon be, and what is wider picture like for military developments in space? Who else could have similar weaponry?