It has been noticed that in most games of the RPG genre uses some form a listing method. This method stores (almost) any number of any item at any time. Some games, however, have found ways to limit your items (like NetHack uses your bulk load as a solution). Perhaps another way to limit your backpack is to use tiles in the form of an array. Tile-based inventorys work in the ways that items are stored in the form of squared tiles. Some items, due to size, can hog up two, three, or even four tiles total. How can this stop the bottomless container? Maybe the designer can include BACKPACKS/STORAGE CONTAINERS as something to upgrade. The better the pack, the more items that can be stored in the matrix. Ask yourself this: how many RPGs have you personally encountered that uses such a system to limit your load? Probably a few have gone through some measures, but most of your games will still have the bottomless backpack.

Their have been several games that use Grid Inventories.

Personally the only game where I ever liked it was xcom, mainly because you were only fiddling around with what you actually needed for one battle and loot was handled separately. Inventory Tetris gets old quickly if I just want to haul monster guts back to the pawn shop in the least number of trips or even worse in jrpgs when you get a limited amount of inventory spaces and they clog half of it up with plot macguffins.

Stay away from them is my vote. Arranging items is a pain. I've used it in the Diablo 2 and the first Deus Ex. If you need a limit on large items I suggest having slots for specific item classes. Say one or two large items (i.e. a two handed weapon) two to four medium items (i.e. single handed weapons) and some number of small items that would fit loose into a small sack (i.e. magic stone and other items no bigger than your fist). If you need to limit it further, have a total weight allowance along with these slots. If you want more flexibility, allow the large item slot to hold two mediums and the mediums to hold two sack's worth of small items. Then let the player use the total spots how he wants.

This may sound worse than the grid system but it gives each inventory space a specific function with a defined size that isn't dependent on the arrangement of the items.

EX, you can hold a spear (L) and a tower shield (L), a short sword (M), a dagger (M), a medium sized quest item (M), and four small sacks (S)(S)(S).

Or you can just have items have weight, and the player becomes encumbered when they are trying to carry too much. I agree that grid inventory systems are terrible. You spend a frustrating amount of time shuffling your inventory items to make oddly-shaped items fit. Or, like in Sacred 2, almost every item only takes up one slot which makes you wonder why they had a grid inventory system anyway.

Grid systems are just not fun. That, along with the fact that you could permanently mess up your characters, was one of my biggest gripes about Diablo 2. I know I couldn't have unlimited space, but grid inventories are just frustrating.

I vote no on "inventory tetris". Whatever it gains in realism it quickly loses in obnoxious meta-micromanagement, and it causes players to have a moment of unpleasant doubt when they think, "What if this awesome sword really would have fit in my inventory if I'd been better at that stupid minigame? Maybe I could have kept the fruit of my labor if I hadn't failed at a totally unrelated task."

Personally I love the Grid Pack system. I hate scrolling through endless lists of items and even when they have sorting options built in they become tiresome. I agree there is some micromanagement to organising the pack but if the amount of items being dropped compared to what you can store is out of whack I think it’s more of a balance issue. Diablo 2 I think had an "auto shuffle" which would sort the items in the most efficient way possible grouping all the spare squares together with a single click of the mouse.

I plan to use a grid system for my games because I believe they can be presented really well and are easy to understand. Some items could be really light in weight but huge in size so you'll need a separate state to measure volume.

How about simply giving all the objects weights in (say) grams and also an "unwieldy" rating. So, coins are light, but not much of a pain to carry. Armour is heavy, but not unwieldy. Spears, on the other hand, are medium weight but unwieldy.

Then put a cap on both the weight and the wieldyness a player can handle. As a bonus, you could wieldyness as a modifier in combat to represent that fact that someone carrying a ten-foot barge pole can't dodge easily.

Size or unwieldiness or some such measurement would be a good abstraction of what the grid system is trying to show without making you arrange things.

Please do step away from calling pole weapons unwieldy in combat. They wouldn't be used if they weren't very effective. 10 foot might be a bit long to handle, but 7 certainly isn't at all and some how I doubt that system would treat them very differently.

Not sure if I understand "inventory tetris" right, but I think it makes sense to somewhat limit the inventory in some noticeable way, both to make the amount of data manageable and to provide extra difficulty or challenge. It is just important that you don't make it permanently annoying.

For example, only being able to carry 5 items or 10 bulk units total where each average item is 2 units and some are 3 or 4 will be annoying if you need to pick up keys or quest items in addition to the items you want to use. Especially if you need 2 or 3 keys in some situations.

On the other hand, allowing a player to carry around 2000 items in a multiplayer game with cutomizable items means a lot of extra traffic from your database backend to the game server in addition to storage. It doesn't make the game easier for the player either, because the inventory will be a total mess. It will also result in "pick up everything" gameplay, which isn't terribly interesting in my opinion.

Lastly, inventory limitations can be an interesting game element. For example, if you can't put certain items in your backpack (say, a longsword or a spear), then you must carry them openly, so these will be visible to others.
That will prevent you from taking them into an area where those items are not allowed, unless you find a way to smuggle them in. Think of the Robin Hood movies where they smuggle their swords in a wagon or hide them under a priest's robe when walk past the guards at the city gate.