I can't think of anyway to use gold properly. It is quite weak if it's used for tools or armour, and because of its rarity, I'd rather not used it for stuff like that. I'm also not really into decoration, so just a gold wall won't really be the answer I'm looking for! Is gold just useless or is there something that only can be made with gold?
I use my gold for enchanted items that I don't use a lot like silk touch shovels for when I need grass blocks. Gold tools mine faster than any other tool and also have the highest chance of good enchantments.
Having clocks around your base can help you if your base is underground
Other items that you are able to craft using gold are golden apples, these give you a nice buff but cost quite a lot. also the golden carrots that can be used for breeding rabbits, taming horses or making nightvision potions.
The "best use" for gold is fairly subjective, but there are a bunch of things that can only be made with gold:
Weighted Pressure Plate (Light) - Gives an analog redstone signal that is equal to the number of entities on it (max 15).
Powered Rail - Increases the speed of minecarts that go over it when it's powered with redstone
Clock - Shows the time of day
Golden Apple - Gives regeneration and absorption potion effects when eaten, 2.4 nourishment value
Golden Carrot - Used for making night vision potions, 2.4 nourishment value when eaten
Glistering Melon - Used for making instant health potions
Gold can also sometimes be traded with villagers for other items, and weapons/armor made of gold have a higher "enchantibility" (better chance of getting good enchantments) than any other material.
You can make Mojang banner with enchanted golden apple.
This is only for decorations this will not help you in singleplayer but if you play multyplayer much servers have shops where you can sell banners or trade to another player.
You can use gold for beacon too if you have much.
There's indeed not that much use for gold in minecraft, other than for decorative purposes because it's "shiny". This can be seen as an interesting similarity to the real world, where the primary use of gold is also for its "shiny" decorative effects, having turned it into somewhat of a "currency for currency's sake" over the history of humanity and its strive for gold.
However, even in reality it has indeed won a bit more practical significance in modern days due to its usage in electronic components (and other technological purposes). And this again relates back to Minecraft, where gold can be used in a few select Redstone components, like clocks, but their usefulness still depends on your personal playing style and you usually don't need them in overabundance. The most important of these being powered rail, which is needed whenever you need a minecart to drive automatically without a downward slope. So whenever you built a piece of rail and want it to be bidirectional, you need powered rail. And seeing how you get effectively 1 powered rail per gold bar, this can get quite gold intensive.
Then there are special food items and ingredients, like golden apples, golden carrots or glistering melons whose use again depends on your personal playing style. Those can gain you some interesting effects by eating or brewing with them, but nothing that is particularly essential for gameplay or can't be downright ignored.
So on the bottom line, the thing that is most likely to eat up your gold resources depends on your playing style. If you enjoy a more construction oriented game, you'd be more likely to spend most of your gold on powered rails, but of course this also depends on if you build much railway in the first place. If you enjoy a more exploration and fighting oriented game, you might want to use the effects of golden apples, carrots and melons more often.
In this situation the most useful items look to be Glistering Melon, used for Potions of Healing; Golden Apples, which provide some useful buffs; and Golden Carrots, which can be used for horse and rabbit breeding or for Potions of Night Vision. Other items you might find useful are Powered Rails and Clocks.
Well, I think that the best use is to craft gold blocks, which you can then use to craft Enchanted Golden Apples (By placing an apple in the middle of a 3*3 grid and filling the rest of the grid with the blocks). An Enchanted Golden Apple (Notch Apple) gives you the Resistance (reduces damage) and Fire Resistance (makes you immune to fire and lava) both for 5 minutes. Also you'll receive the Regeneration 5 (heals you very fast; possibly 3.33 half-hearts per second) for 30 seconds and absorption, that gives you 2 additional (yellow) hearts to your health bar, that cannot be healed, for 90 seconds. So, it is extremely useful to eat one in difficult battles, such as an army of angered zombie pigmen or the wither. (Also written in other answers) Other important uses may be for beacons and powered rails.