It would absorb damage at the same time allow for only one handed weapons to be used with it. Perhaps one handed ranged weapons take a penalty on accuracy, and one handed melee weapons as well to balance out the extra bonus of more defense.
Different shield types could had different strength requirements.
Perhaps even when a shield is equipped you cant zoom in but rather you automatically get the chance to block an oncoming attack, just like oblivion blocking with the right mouse button, perhaps if your timing is right you increase you damage threshold with a successful block and if it you failed to block would you decease your damage threshold.
As for what kind or crazy shield here are some ideas,
Could be
a car door (yep like the Behemoth carried) from Elvis's gold plated Cadillac,
a trash can lid,
a hub cap,
a super mutant head,
a mirelurk or nukalurk shell shield that glows blue from the Nuka Cola Quantum
i giant piece of steel (if you had major strength to carry it)
a door from a fridge from the junk year,
or my second favorite a riot shield!
and my first favorite idea, get one from a random encounter!
i love melee and HTH but i miss not being able to pick up a shield
i miss my Sword and Board play style and wish it could be in FNV,
Thanks guys.