Skip the boring stuff. Games such as Leisure Suit Larry: Magna Cum Laude and Onimusha: Dawn of Dreams allow players to bypass minigames when they become tedious. Letting players set their own agenda rather than forcing them to line up dots for hours means that games can cater to different moods, rather than simply different abilities.
Time spent shouldn't be wasted. Ever run around aimlessly for hours in an RPG only to realise you've achieved nothing? By tying in achievements to measures such as play time or distance walked, as in Dragon Quest VIII and Gradius V, players become rewarded for simply playing the game. Even aimless sessions allow players to achieve something.
Gradual gratification. By constantly achieving small goals as part of a larger picture, players stay motivated. Jewel Quest has a literal 'big picture' -- an image which is progressively revealed by completing levels -- but even small things like changing the flags of a newly captured town in The Outfit can leave a mark.
Empowerment. World domination is but a step away with intriguing game mechanics that allow players to have an impact on other players -- and their friends, and their friends, and... From zombie outbreaks in Infected to designs spreading around the globe in Animal Crossing: Wild World, viral content (especially easily trackable content) leads to power and greatness.
Easy heroics. Sometimes working your way up the ranks isn't good enough. In Guild Wars, the character builds of the world's top players are available for newbies to try out from the very start; Project Gotham Racing 3 only allows you to race top-end cars, rather than the usual racing mechanic of starting slow and working up. In today's instant-gratification culture, the immediate power encapsulated here is seductive, although games like Guild Wars retain the option to start at level 1 and recreate the glory of the best.
Art and Me. Creativity and self-expression in games? Not just a pipe dream. Pac Pix, Magic Pengel and Okami all combine drawing with games in odd and entertaining ways -- and being able to see your creations come to life and have an effect on the game world is rewarding. The passive nature of this integration (draw once, reap the rewards later) puts it in contrast with other games that actively encourage you to create within the world (such as Animal Crossing and even Second Life).
Showing off. The simple ability to take screenshots within games -- maybe marking particular achievements, or cool moments -- and share them with others is a PC staple, but what about consoles and handhelds? Loco Roco and Rumble Roses recognise that sometimes people just want to record pretty pictures, but being able to save screenshots from consoles is rare.
Smaller design ideas. While Margaret thought these seven ideas were particularly 'stealable', there are also a load of tiny tweaks that make games just plain fun. For example, having a consistent "we're red, they're blue" mentality in multiplayer games; the 'sell useless items for cash while out in the field' feature of A Bard's Tale; the ability to both co-operate with your friends and smash them to a pulp in multiplayer Zelda.
The most stealable idea? Create your own new ideas, design tweaks that fix those problems that get you miffed. Copying other strokes of ingenuity is great, but originality's even better.
Margaret highlighted a wide range of design issues that some gamers overlook and others praise; game design isn't a perfect science, and new shortcuts, tweaks and improvements are continually introduced by new titles. Even innovation on a small scale is innovation; some of the improvements listed above managed to turn unplayable titles into playable ones, so never underestimate the power of a single small design decision.