Apart from camera and lenses there are one or two accessories that landscape photographers really can't do without. So, for your edification I've had a rummage in my camera bag and made a list....
Comfort should always be a priority when choosing a camera bag. I can wear mine all day without it being too much of a burden. Tamrac 5788 Evolution 8 Photo/Laptop Sling Backpack Bag
A camera bag really is essential unless you want to carry everything in your pockets (and you don't, you really don't). The funny thing about camera bags though is that they're very personal things. They have to fit you comfortably, not just for a few minutes but potentially for several hours. This makes it hard to say which is the right one for you until we get to know each other better. Personally, I'm not keen on the over-one-shoulder type. I much prefer a two-strap job. If it has a hip belt to take some of the strain of my shoulders than so much the better. Oh, and it has to have compartments. Lots of compartments to keep everything in order and easily accessible. However, your needs may vary considerably.
Manfrotto 055XPROB Pro Tripod
An essential piece of kit for the landscape photographer. Ideally it should reach up to eye-level without raising the centre column too high if at all. But it shouldn't be so heavy that you leave it at home by choice rather than by accident.
Hotshoe spirit level
Polaroid Hot Shoe Three Axis Triple Bubble Spirit Level
My camera has a rather nifty built-in spirit level. But do you know what? I just don't trust it. I'd much rather use a spirit level attached to the camera's hotshoe. After all, generations of joiners and builders can't be wrong about their usefulness. Who's ever used a camera to check whether a wall is straight?
Nikon 25395 MC-DC2 Remote Release Cord Canon RS-80N3 Remote Switch
Oddly enough I tend to use my camera's self-timer function more often than a remote release to fire the shutter. But that's just personal choice. My remote release has one use and that's for locking open the shutter during long exposures in Bulb mode. It's so much easier than holding down the shutter button by hand for lengthy periods of time. Trust me on this.
There are two spare batteries in my camera bag (and one in the camera of course). In summer running out of juice is less of a problem. Come the cold of winter though and batteries are less efficient. I have used all three in one long and extremely cold session. The key of course is to make sure all your batteries are topped up before leaving the house.
Compass and Map
Suunto M-3 D/L Pro Compass
A good map of an area is an invaluable both when planning a shoot and for navigation when I heading on the shoot. I could of course replicate these with a smart phone but I'm old-fashioned enough to prefer a paper map. Partly because it never runs out of power but mainly because you can't swat flies out of the way with a smart phone.
Nikon 8072 Microfiber Cleaning Cloth
Clean, lint-free lens cloths are invaluable for keeping the front elements of a lens clean, particularly when it's raining. I also keep a couple of absorbent cloths in a pocket for drying or cleaning the camera body too.
UltraPro 77mm Variable NDX Fader Filter
I like to keep it simple when it comes to filters. In my bag there's only three ND grads (a 1, 2 and 3-stop hard ND since you're asking), a UltraPro 77mm Variable NDX Fader Filter and a polariser. The grads and polariser are all made by Lee and fit into a Lee Foundation filter holder. Oh yes, there's also a starburst filter in there too. I really don't know what I was thinking of at the time.
Lastolite LL LR2034 20-Inch Collapsible Reflector
A foldaway reflector is a useful thing to keep in a bag just in case I fancy doing a spot of close-up work. The reflector can either be used to lighten shadows or to cast a shadow on the subject. Both uses help to lower contrast to acceptable levels.
And that's pretty much it. Even if my camera bag is comfortable, I really wouldn't want to carry much more. Besides, I like to leave room for sandwiches. However, do let me know below if there's anything that I've missed out that you find invaluable.