If you like TD, people seem to thing geodefense swarm is hard. I actually found the first one harder but i guess it depends on wheter you like em open or fixed. Anyway their both great games, try them.
i thought warfare inc and quantum collapse to be relatively hard (both RTS) and very fun to play ( warfare inc has multiplayer) i also agree with GeoDefense (first one) It's very fun and has a puzzle feel to it. I'm having a hard time with swarm but in reality I'm not really trying, there's been too many good games lately, i cant even get started on a lot.
There does tend to be a significant dumbing down of difficulty on the app store. This is obviously because most players are kind of casual and devs are understandably keen to maximise appeal. There are a few that standout as difficult-but-cool though. I find games based on mastering controls very rewarding. iPlutoid: Very tough at first, not just the controls but also getting your head around the true-3Dness. This makes it all the more fun when you get the feel of it. Eliminate: Enough threads of it's own but I find it hard and am hoping to actually find it fun soon. Puzzlemaniak: 20 great puzzle games, all of them VERY hard on the toughest levels. The most underated game on the app store. Ground Effect: Yeah, it's my game and it's not out yet (hopefully the next few days) but like any good driving game (personal opinion) it's absolutely all about getting the feel of the controls until what once seemed impossible becomes second nature.
+1 Lunarcy Also Orbital, Eliss, Aves, Darkest Fear, and Alice's Adventures: The Rabbit Hole of Death all get very difficult. EDIT: I forgot Squareball - but you can't wuss out and play it on easy!
Lol i actually found darkest fear becoming easier as the levels progressed. The first boxpuzzle on the second level was like wtf! for me. It took me an hour or so to figure that out =) but from there and on the rest was easy (and funnier for that sake). Only thing with that game was the horrible controls.
real racing on A division, they can get annoying Eliss when you first start playing and are not used to managing 20 things on the screen at once SPACE NINJA, hardest game I've played on the iPod
I personally found "1112" to be hard (I'm sure you can find cheats online, but that rather defeats the purpose). And yes, Eliss is the best intellectual game out there. Thanks for all the game tips. I just bought Puzzlemaniak, Lunarcy, Archrobo, etc.
Avoid Hitting Piano can be really hard, but it is not an endless game like Canabalt (also a hard one) But you might want to throw your ipod out of the window (that kind of hard)... cheers
Alien Glyphs - in survival mode if you never play it before it wil be very hard to play for you, but if it is easy - wait for update we prepare Insane difficulty