I second the Easton Lightspeeds. They are a lot tougher than I thought they would be and they are light. Of course if you want really light you could always shoot the High Country arrows at I believe 5.5 gpi. That's the lightest I have seen yet. Don't know how durable they are though.

As far as tips for carbons/3D targets are concerned I saw THESE while in Bass Pro the other day. There is a typo on the webisite it says $5.99 for a 3 pack, but they actually come in a package of 6. Still pricey though.