We've seen the last year or so filled with games that are requiring 6GB of RAM or more, such as Assassin's Creed: Unity, Watch Dogs, Call of Duty: Advanced Warfare, and more. Well, CD Projekt Red's delayed title The Witcher 3: Wild Hunt also requires 6GB of RAM.
The developer actually recommends that you have 8GB of RAM, but 6GB of RAM is required at a minimum. As for the CPU side of things, you'll need an Intel Core i5-2500K or an AMD Phenom II X4 940 to run the game at a minimum, while the developer recommends gamers to have an Intel Core i7-3770 or AMD FX-8350.
The GPU side of things isn't too bad, with the minimum requirements at an NVIDIA GeForce GTX 660 or AMD Radeon HD 7870 while the recommended specs want you to have a much higher-end GTX 770 or R9 290. A 64-bit version of Windows 7 or Windows 8/8.1 is required, as well as 40GB of free HDD space.