IPhone 4S without a carrier?

I was thinking of buying a iPhone 4S to use just with Wi-Fi, is it possible I can do that without having a carrier or paying for a plan?

Get an ipod

Sure you can do that, if you don't want to make any calls with it though you may want to look at an ipod touch or ipad or ipad mini instead, they will be cheaper and you can still do all of that over Wi-Fi, including using imessage etc.

Here is the unlocked iPhone
4Shttp://store.apple.com/au/buy/home/shop_iphone/family/iphone4s
You will need to buy a micro Sim card to activate it but this can be a prepaid one that you can throw away when you have done this
If your not going to use it as a phone then I would suggest getting an iPod touch instead because it would be cheaper.