Many Christians (myself included) automatically default to the cross when answering that question. I’ve decided it’s unhelpful. The cross by itself is insignificant (symbolically) – Jesus could have died on anything, they could have drowned him, burned him, or drawn and quartered him – the cross was just a functional means to putting Jesus to death. The resurrection (as Paul argues in 1 Corinthians 15) is where it’s at for Christians. If there was no resurrection I wouldn’t be a Christian – and Paul says I wouldn’t be atoned for either.
The empty tomb is a heaps better symbol. It just doesn’t look as good on a necklace.
There’s a bit of a difference between “died and was raised” and “died, AND was raised” – I think too often we fall into the latter category – and indeed change our emphasis to “DIED…and was raised” – I don’t think Paul does that in 1 Corinthians 15, and I don’t think the creedal confessions do that either.
I’ve been thinking about this after a news report called Good Friday the most significant day of the Christian calendar, and following a couple of conversations, one in the real world, and the other at Gary’s blog where he warns about “bait and switch” gospels.