Bought the Logitech MK260 Wireless Combo  (Keyboard & Mouse) from Challenger for S$39 (member’s price is S$36.90). It is one of the cheapest branded wireless keyboard and mouse combo that I can find in Challenger. The other option is Wireless Desktop 800  which is retailing for S$39 (member’s price is S$37).
Some notable features of the Logitech MK260 includes use of 128-bit AES encryption for encrypting data transfer between the keyboard and receiver, spill-resistant keyboard and battery life that can go up to 24 months for the keyboard and five months for the mouse.
The keyboard is powered using 2x AAA batteries while the mouse is powered with 1x AA battery. I wish both of them use AA batteries instead of having two different size batteries.
The reason I chose wireless is because I will be using it for my Raspberry Pi  and it has only two USB Ports. I need to keep one USB port free for my media USB flash drive, so that leave me with only one available USB port.
If you are getting a wired keyboard and mouse, it will take up both USB ports, so wireless is the way to go unless you get a keyboard with a USB hub built-in.
Logitech MK260 Wireless Combo – Box Front
Logitech MK260 Wireless Combo – Box Back
Logitech MK260 Wireless Combo – Box Contents
Logitech MK260 Wireless Combo – Keyboard
Logitech MK260 Wireless Combo – Mouse
Logitech MK260 Wireless Combo – Keyboard & Mouse