A 'gizzit' or Giz-it can be a number of things, but is basically a freeby, either blagged or freely given - usually the former and rarely the latter. The is a thin line between something that is donated by the 'gizzer' and something that has bee proffed by the 'gizzee'. Squaddies thrive on gizzits and in some places gizzits can become de facto currency.
Leaving a box of complimentary items - whatever they may be: pens, baseball hats, t-shirts etc. - with a sign saying 'please take one' is a red rag to a bull, and its contents - intended for many - will be stripped bare within seconds... by the few.
Corruption of the well nown squaddie phrase, "That's a shiny - gizzit 'ere !"