If he overnight camps/hunts in the cold, camp booties are nice. Light and warm and comfortable on your feet at the end of the day. Same with a pair of Crocs. They do not weigh much but help in water crossing and airing out your feet after a long day of hunting...
Like Elkchaser24x7 noted before, a gift from the wife regardless of what it is will be treasured. So pick from the heart and give from the heart, he will appreciate the gift no matter how big or small...