The Phantom Quickdraw is the lightest on the market.
Phantom is a super specialised biner, following the "light is right" path but crucially using I beam technology and 7010 aluminium to keep the strength high.

Closed Gate Strength: 23KN
Open Gate Strength: 9KN
Karabiner Weight: 26g

Available with a choice of sling lengths:
12cm Dyneema Sling
18cm Dyneema Sling