First Field Dressing.
Sterile Dressing which has two tapes attached, used for securing the dressing in place. Comes in two sizes and is contained in a little brown packet (Hint & Tip: If you're in the brown stuff the inside of the packet is sterile and can be used to help stop severe bleeding). Each Squaddie should carry two of these little babies (usually in the top left breast pocket of their smock). Will absorb a pint of liquid, as some squaddie in Bosnia found out when a drunken mucker dropped one into his beer (note: it's still sterile once wringed out due to the alcohol killing bacteria. Beer tastes minging though).
Probably one of the few things that we use that the NHS would love to have.