A Sniggy Pig is one who means a lot to another. It is almost exclusively used in an affectionate context but can be incorporated into everyday language also. Similar to other terms of affection, it is assumed one will only have one 'Sniggy Pig' at a time.
'Who is the girl you're with in that photo?'
'That's my SniggyPig'
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.