There's no way I would go on any hunt without my rangefinder and it wouldn't matter if the guide had one or not. I've had issues with the Leica's in the past on Dall sheep so I use a different brand now just because of it.
Lightweight rain gear as mentioned above is a must, I haven't tried it yet but I've heard great things about the Westcomb which utilizes eVent, it's light and breathable gear.
I also am not a fan of the anti-shok trekking poles and my Leki Makalu's have worked well for me.
Do yourself a favor and bring a good camera and take lots of pictures, 20 years from now you'll be glad you did.
I also like to bring a bandana with me for those hot days, soak it in a creek and wear it under you hat.
The suggestion of camp shoes is a great idea and I never go on a hunt without them.
I've become a big fan of merino wool, specifically boxers and socks, they will keep you warm and dry on those cool mornings.
A good pair of binos is a MUST, I've been using a pair of Swarovskis in 10x42 for years and love them but they are a bit heavy. Just make sure you bring the best you can afford.
