If you're planning on using a shield as a giant,
you should only look at Two Handed Swords because they're just better in terms of enchant access and damage.
So in that point the best weapon to use with a shield is arguably the
Dragon Fang.
If you land Max Roll with the Artisan Upgrade it can reach a Max Damage of
120.
The Sword of the Goddess isn't too great because, if I calculated right, it can only reach a Max of 89.
Highlander Claymore is decent and it gets a Max of
108. That's just -12 Max compared to Dragon Fang, and also it has higher Critical Rate (29%) than Dragon Fang's measly 6% Critical rate if that matters for you.
Also you may also want to consider
Demonic Death Penalty Blade. Despite what people say about this sword, it's fairly great if you obtain Max Roll on Artisan. You can get a Max of
113 and also it has very high critical rate.
If you can't really "choose" I'll just say that
it really doesn't matter which one you use. They're all great swords especially for Giants+Shields.
Edit: I forgot about Bhafel Slayer (probably because it's extremely rare due to scarce materials/dragon huntings). It's more or less the "endgame" Two Handed Sword if you manage to get an 81 Base Max created. That plus Level 2 Piercing almost makes it a Lance.
One more thing:
Giant Only Swords are categorized as One Handed Weapons so if you're looking for damage, don't use them. That goes for other one handed weapons. Two Handed Swords are the best for Giant+Shield (excluding Lance).