Bombs: They go ka-boom.

Cursed Items: When you equip them you get cursed; you have to defeat the curse before it consumes you. A sword that drains your health until you have slain a certain number of foes, or a helmet that tests your mettle by pitting you against hordes of enemies while blinded. Sentient equipment that refuses to be wielded by just any bumbling adventurer!

Hidden Enemies: I know that's not really unique, but it will help gameplay a lot. Maybe a certain kind of Antlion or Skeleton which is initially digged into the ground and will only show up as soon as the player is within a certain range. Maybe aswell something as those attacking treasure chests seen in Torchlight.

Economy: In most, if not all, ARPG's economy does not play a decisive role. In a typical ARPG, the only form of economy is buying and selling items from and to the shopkeeper/dealer. This will typically not influence the prize of these goods, neither will the dealer/shopkeeper ever run out of stock. However I think it could be quite interesting to have an ARPG where economy is an integral part of the game. Maybe the economy could even influence the course of the game. I think it would atleast be worth a try.

I think this has already been mentioned somewhere, but...

Combos/Attack Chains: Instead of vertical chop, vertical chop, vertical chop, vertical chop, etc.; what about vertical chop, slash right, slash left, stab, etc.  Better skill in physical attack could unlock longer combos, in the style of Dynasty Warriors.  Ranged and magical attacks already have variation and flavor to them, and this could help bring some of that to melee characters (instead of beat, beat, beat).  The main drawback here is a lot more animation and rendering for all the equipment.

Other protagonist races: Allow the player to select a dwarf, orc, or whatever you come up with for plausible PC races.  Maybe even just different groups of humans with different abilities.  It would be nice to avoid the "race only matters for the first couple levels" problem that happens in some many RPGs, though.  Maybe these could be analogous to classes in Diablo 1, where you could still gain different abilities but each class was more adept at certain things.  Another possible drawback: why play a dwarven mage if dwarves suck at magic?  Balancing different builds could be problematic.

buildingblocks and assembly: it might just be like crafting items, but why stop there. make vehicle and assemble them, work out the wire's ware the fuil thank sude be, anything, compleet controle.
depenting on wer u get hit u can lose parts or brake them if not protected

wel its just a little idea, hope it helps somone out 

Flare has active shielding, and agreed, it's pretty neat; more fun skills that interact well with this would be sweet.

Neat thread, thanks for starting it!

Yeah right now Flare plays it pretty safe. It would definitely be nice to change things up a bit IF the results are genuine fun and make the gameplay actually interesting. Active shielding is an example of something not commonly done but can be fun if done well. It doesn't detract from the fun/flow of the moment-to-moment play.

Some ideas I'd like to think about:

What if vendors don't buy the crap you find in dungeons? What if instead you tore them down to raw ingredients (wood, steel) and could use them to craft/alchemy new things? Or, what if you could turn in these raw materials for reputation, or a war effort, or rebuilding a town, or bonus xp.

What if you got an experience multiplier for defeating enemies quickly? Or for killing enemies in a row without taking damage? Some kind of "combo"ing would be fun, where playing a certain way or with skill is rewarded. What if powers were designed specifically to combo together? What if combos built meter that could be used for crazy powers? What if basic attacks restored MP and big attacks used lots of MP? Anything like this to add to the dynamic of combat could be interesting, especially for melee combat. More melee attack animations could be worth it.

Here's one I really want. I liked experimenting with Powers unlocking according to your base ability scores, but it's very limiting and hard to get right flavor-wise. I think I'd prefer having spendable points to buy/upgrade Powers.

This might be getting too cute but: we have base Ability Scores (physical, etc), Powers, and Items. Each can make your character more powerful. It could be possible to make a system that only uses one of these. E.g. there are only Items, and you build your character completely based on what you're wearing. Find a Staff of Fireball if you want to shoot spells. Get +10 health armor instead of raising your Physical score.

I think a good art direction could help add some needed atmosphere to the game. We're working on that.

This is definitely coming, but the game needs monsters that move differently. Currently monsters only chase the hero dead on. New flying monsters could dive/swoop past the hero and travel along curved paths. Ranged enemies should learn how to run away. Some monsters should have movement tricks (e.g. go through walls, burrow underground). Some monsters should be good at blocks and counter-attacks. Maybe some monsters only move when the hero does something (e.g. look away, move, attack). Maybe some monsters move in specific patterns and it's better to avoid than attack these creatures.

Traps! Now that powers can be spawned from map events it should be easy to make lots of classic traps: spikes coming from the floor, saw blades that race along the ground, dart traps triggered by pressure plates, bladed pendulums, firebreathing statues, teleport traps, rigged chests, etc.

More environmental lore. It's very dull to tell a story through NPC monologue. It's much more interesting for the maps to tell the story. Those books I currently have are a weak example but they help. More runic carvings, secret scrolls, old statues etc. should tell the full story. Also it's much better if the visuals tell the entire story without involving words. Example: a carefully placed skeleton corpse and broken wagon with spears sticking out of it -- don't need dialog, the player can put together a more interesting story in his head than the one we have to tell.

Mini Games

Basically when you Fish,Lock pick,Try to make a deal with a Goblin Chief ,draw magic from Artifacts you play a mini-game and depending on the outcome you get the appropriate reward.

Example :

The player comes across a giant blue shard coming out of the ground and if he/she whats to tap in to its magic energy he needs to play a memory game similar to the 90' Simon machine. Depending on the score he will get one of those bonuses.

1.Replenish 50% Mana

2.Replenish 100% Mana

3.Replenish 100% Mana and 50% Hit Points

4.Replenish 100% Hit points and Mana

5.Replenish 100% Hit points and Mana and gain a one time +5 bonus to mana pool

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Take a look at this opensource html5 game (it's amazing, released today) http://operasoftware.github.com/Emberwind

Maybe it's possible to implement Flare in Browser, it will give it advantage in user base (no install, runs everywhere with a single click away) and in developers community, because almost everyone knows JS.

What makes you think that that game is open source?  I looked through their site and it doesn't seem to say anything about open source or any open license.

Alexey Petrushin: When I started Flare I ruled out doing it in browser because of the size of the assets. Load times and throughput requirements would be quite high. Who's going to foot the bill for a server for a game like this?

With it being downloadable and GPL, I can use up all the download throughput I want on GitHub for free.

> What makes you think that that game is open source?

You are right, I also noticed a little later (after posting this message) that there's no license. Sorry for this delusion.

But, the sources are there, and - the proof of concept. I personally had some doubts that there will be enough performance in HTML/JS to run such games, but as it turns out - it's enough.

> Load times and throughput requirements would be quite high. Who's going to foot the bill for a server for a game like this?

Yes, You are right, hadn't thought about it. But as far as I know asset-hosting has low requirements on the server + caching assets in browser may also lower bandwidth. So, maybe it would be possible to rent some small VPS (for example, linode is about 20$/month) with unlimited bandwidth option and it will be enough (but I don't know this for sure).

Didn't run very smoothly here, like most other JS games I've tried.

Continuing on catapults, some sort of siege-scenario could be fun, with plenty of interactive props and map events. Not really a core gameplay thing though.