The Shepherd's Cross evokes images of a gentle shepherd looking after docile lambs. But is has a very different meaning to that.
The Shepherd's Cross is a not-so-common stylised cross which some may confuse with the more commonly seen Chi-Rho Cross. It is also important to distinguish between a Shepherd's Cross and a bishop's crozier, which is simply a symbol of prelatic authority and jurisdiction. (See also Bishop's Cross.)
The Shepherd's Cross is a useful reminder for those times when we feel lost, empty and don't know what to do, we can imagine Jesus as a Shepherd, guiding us and looking after us.
But the symbolism runs deeper than that:
The Shepherd's Cross links to the parable of the Good Shepherd in John 10:11-18. The story starts by telling us of the sheep farmer who hired a day labourer to look after the flock. When a wolf came, the hired hand fled to save himself, since his life was worth more to him than a few smelly sheep. The wolf, of course, was rather attracted to the smell of sheep. The parable then goes on to portray Jesus as the good shepherd, who doesn't flee when the wolf comes. Instead, Jesus lays down his life for the sheep to protect them from the wolf.
In this story, we are the sheep and the Devil is the wolf. However, this doesn't mean we should behave like mindless, docile lambs. Just as God doesn't walk around with a shepherd's crook, and the Devil is considerably more fearful than a wolf, the parable is to be read metaphorically.
So that's the symbolism of the shepherd's crook. The cross, of course, symbolises that Jesus did indeed die for us, his flock.
(See the similar Patriarchal Cross and also the Meaning of the Cross.)