King of Fighters XIII will be the latest game added to US PlayStation Plus subscribers' Instant Game Collection. The Instant Game Collection is an assortment of both full retail and PSN-only titles made available to PS Plus subs to download at no extra charge.Last week saw the addition of NFL Blitz to the collection, and tomorrow's PS Store update will add King of Fighter XIII to that list. In addition, The Revenge of Shinobi will be put on sale for just $1 to PS Plus subs this week, while new release Derrick the Deathfin will go for $5.59 - and 30 per cent discount on the normal $7.99 everyone else will pay. Instant Game Collection has proved a huge hit with PlayStation gamers, as Sony accredited a surge of sign-ups in June to the initiative's announcement at E3.