Ios 5 came along with a new set of keyboards: emoji
emoji are like smilies, but there are hundreds of them

you can enable them on your ios 5 or ios 6 device:

goto settings > general > keyboard > keyboards

click ‘add new keyboard’

scroll to emoji and select it.

now you will notice a new key on your keyboard next to the left shift ( a sort of globe symbol )

click that and you get the emoji!!