A lot of what food is available to you depends on the size of your city. If you have specialty pet stores then you have a wider options. The second best option is Farm and feed (tractor supply co, etc) and last being Petco or Petsmart. You will likely not find anything decent at your grocery stores. The best food for your dog is the food it does best on. Not every dog, like stated above can handle the same foods based on nutrient density.
I personally have fed Orijen Large Breed Puppy and Earthborn Hollistics Primitive Natural to my growing EM and am incredibly happy with the results. Slow steady growth, he enjoys his food, and the ingredients are, IMO, the best available in commercial dog food. This does not mean it will work, or has worked for every puppy, but it is what works for us.
Here is a list I came up with :
If you are looking for a no grain kibble (most have locators on their website to find retailers near you):
Orijen - Large Breed Puppy, Adult, 6fish, or Red Regional - organic, high quality ingredients, 6 unique meat sources. Found at pet specialty stores
Taste of the Wild- great quality at a cheaper price, 5 unique meat sources, found at many local feed and farm stores. 3 formulas to choose from.
Earthborn Holistic: All Grain Free Formulas. Depending on allergies you may want to forgo Primitive Natural due to chicken inclusion.
Fromm Grain Free Surf and Turf- great quality food from a great privately owned company. They use top of the line ingredients and while their prices are on the high end you are getting your monies worth. Can be harder to find, but look for it at your specialty pet food stores.
Innova: EVO: - one of the best grain free foods out there. High calorie, high protein (with 4 unique protein sources), low carb and packed full of nutrients. Limited Ingredient formulas. While it is a great option for a grown Mastiff, it is not a balanced formula for a growing puppy.
Merrick Grain Free (Previously Before Grain): Buffalo, Salmon, Chicken - very good quality food made by Merrick but new addition as of last year. Numbers have changed to make this only appropriate for adult Mastiffs, over 2.3% calcium to 2.5% calcium. Good option for a full grown adult. Not appropriate for growing puppies.
Acana -Grain Free - this food has 3 unique protein sources and is of the same makers of Orijen. It is a more moderate food in terms of calories and protein but has less meat content as well. Potato is the second ingredient in this formula.
Instinct- Rabbit - the other instinct formulas have too high mineral counts for a growing pup, but the Rabbit formula is right on the mark. It has top notch ingredients and a unique protein source. It does not contain chicken, other than chicken fat and is a nice kibble for a dog with allergies.
Canidae ALS Grain-Free- good quality 4 unique meat sources, found also at farm and feed stores, good price for the quality and 2 formulas to choose from.
Wellness Core- great quality ingredients but high price tag, comes in adult, reduced fat and ocean. I have found ocean harder to find. Often problems with dogs wanting to eat the food. Apparently not the tastiest. Petco.
Blue Buffalo Wilderness: Duck, Chicken and Salmon - New improved formula that is a solid product. Higher in calories and more suited for an adult Dane then a growing puppy, but the only grain free option that PetSmart carries. Petsmart.Petco.
Go! Fit Grain Free- Great quality grain free Adult formula. Multiple protein sources and first 6 ingredients are meats and 2 of those are meals. Impressive formula but not suitable for a growing puppy.
Natural Balance Potato and Duck or Sweet Potato and Venison- Not the best choice but if your location is remote and your pet has allergies it could work for you. Limited ingredient formulas, nice for sensitive stomachs and allergies. Petco.
Nature's Domain (Costco)- Very similar to ToTW Pacific Stream but a little bit lower in quality. Great option for an affordable grain free and on par with Natural Balance but for around 25bucks a bag or so. Costco
NutriSource Grain Free: Medium quality grain free option with 2 meat sources chicken and fish meal. It is a little heavy on the peas with the 3rd 4th and 5th ingredient all being a pea source which would likely put it up there in the running for top ingredient with chicken.
Grain Inclusive:
Artemis - One of the best quality grain inclusive foods on the market. Great quality ingredients and several options for formulas.
Acana - several different grain inclusive options made with organic. local Canadian ingredients. have 3 unique protein sources in each.
Earthborn Holistic- Good quality Puppy Vantage formula and formulas for adult dogs. Petco. Feed store.
Go! Sensitivity and Shine- Good grain inclusive options with novel proteins and oatmeal or other unqiue carbohydrate sourcs. Good for a dog with allergies.
Fromm: Any food from their product line is top of the line. They are a privately owned company that focuses on quality and is a higher price tag but worth the cost. Can sometimes be found in specialty pet stores.
Canidae ALS- great ingredients and found at farm and feeds. Good cost per bag and a solid company. Not good for sensitive stomachs and not all dogs can handle this food, I suggest a small bag to start with to make sure it works. *This is one of my favorite grain inclusive formulas* Feed stores.
California Natural: High quality limited ingredient kibble. Great meat content. Harder to find and pricey. Often found at specialty pet stores.
Chicken Soup for the Dog Lover's Soul Large Breed Puppy - Great food for the price. Quality ingredients and great meat content. Not great for sensitive stomachs and I would suggest a small bag to try out before purchasing and commiting to the lable. Also found at farm and feed stores.
Innova - top of the line dog food with great ingredients but pricey. Often found at specialty dog stores. They have a few different formulas inclusing a red meat formula.
Merrick: Has many different flavors and seems to be quite tasty. Quality ingredients and great meat content. Very cutesy names and priced around the same as the lower end grain frees. Uses a good amount of grains but they are on the higher quality scale. Uses around 4 unique meat sources as well. Found at pet specialty stores and farm and feed stores.
Solid Gold Hund n Flocken(puppy): designed based on diets of European Great Danes years ago. It is pretty heavy on grains but they use high quality ingredients. You are looking at a nice price tag on this brand tho. Petco.
Wellness 5 mix: same taste issues but great ingredients. Carries about the same price tag as the CORE label but has a few different options as far as formulas. Petco.
Mid- range Grain Inclusives (Quality of Ingredients):
Eagle Pack Hollistic Large and Giant Breed Puppy: Has a slightly higher meat content than the Original and does not use corn in this formula. Can be hard to find depending where you live and I would look at specialty pet stores and farm and feeds. It carries a pretty decent price tag as well.
NutriSource: I like their Preformance Formula but I do not like the inclusion of beet pulp or how high it is on the ingredient list. Middle of the road option
Eagle Pack Original Large and Giant Breed Puppy: Often used by Dane breeders because studies were done and it was specifically made for the giant breed puppies. I personally am not a fan of the ingredients, but many Danes have been raised on it sucessfully. It simply has too many grains and corn to be higher imo. Pricey for the ingredients.
Go!Daily Defene: Only 1 to 2 named meat ingredients, but use rice and oatmeal for carbohydrate sources
Precise Precise Plus: the new endorsement to replace Eagle Pack by The Great Dane Lady. It is a decent kibble but lacks in quality. Grain heavy. I am not sure where it is located. Very similar quality and composition as EP.
Blue Buffalo: They make a few formulas that are of decent quality and very accesable. They can be found at Petsmart and petco.
Kirkland Chicken and Rice - mid range dog food at an affordable price. It is found at Costco
+ These are the commonly available food options off the top of my head. I am sure there are other good options out there.