I just started Damascus Gear: Operation Tokyo on the train this morning, and I have to admit I'm really enjoying it.
It's a third-person, mech/action/loot game where the story and characters are barebones, but it all seems to work well as a game optimised for portable play. It saves automatically, and you can tear through each mission in a couple of minutes. Each mission consists of a simpy drawn (albeit repetitive) 'dungeon' of urban streets, with you tracking down a rendevous point, killing key enemy units, that kind of thing. Friendly AI is poor but your mech controls brilliantly, so you barely notice them wandering off in the wrong direction.
Face buttons control your three weapon hardpoints, and moving while attacking allows you to strafe. Interestingly, you have two boost buttons- holding R allows you to boost forward for long periods of time to cover ground, and pressing x allows you a short boost in any direction, effectively a dodge. L is used for repair kits (essentially healing potions). It's a control scheme that is both functional and elegant, anyone can be throwing a mech around like a pro after a few minutes of play, and that's before you get into the cycle of equipping found parts, selling what you don't need, trying out different loadouts, replaying missions for better ranks.
Mech fans will love the traditional use of optimising for offensive/defensive power vs weight, plus the choice of weapons across your two primary, one support and one backpack hardpoints is extensive. Lasers, flamethrowers, homing rockets, rifles, swords etc. I even tried out a double-melee loadout, which was hilariously viable, at least for basic mobs. There is also a trade-off regarding vision in missions, which closes in when boosting.
It's £7.99, and well worth it at that price. Presentation on title screens, story etc is minimal, but the core game is highly addictive and great for short bursts.