Indie Pack of JoyI recently purchased an indie pack from Steam, which contained three notable games, The Path, World of Goo, and Braid. The latter two are rather joyous puzzle games, while the former is an art game. I haven't played the Path much yet, as I think it requires time spent thinking about it, and it also may be super depressing.
I can, however, recommend both World of Goo and Braid.
Braid is a clever little puzzling platformer, with the main character having the ability to time travel. Each world that you travel through has its own shtick, with everyone moving in reverse time to you in one world, and time travelling in different directions depending on which way you are facing. Its intelligent stuff, and for the most part the puzzles are fairly intuitive. Sadly this isn't always the case, and there are some frustrating puzzles that really don't make much sense without a guide.
The game also suffers from a leetle bit of pretension, and while the overarching plot is interesting when explained, it doesn't really mesh with the gameplay at all, other than in a VERY metaphorical sense. One of the advantages of that is that you can utterly ignore the plot, so its not all bad. One example of pretension is that the official guide for Braid asks you not to look up a guide. I cannot imagine anything more designed to make me look up guides... There is a difference between knowing the solution to a puzzle and executing it, and some of the puzzles become irritating when you know exactly what you need to do, but are having trouble executing that.
World of Goo, on the other hand, is an absolutely joyous experience. The plot does not take itself seriously at all, and integrates into the gameplay in a loving and ridiculous manner. The game is based around goo balls that can be used to build structures, which you use to get from one place to another. The genius comes from the sheer variety of challenges and different goo balls that enliven gameplay. The game is gorgeous to look at for all its 2d sensibility, and rarely drags.
The puzzles are well designed, and clever, using a combination of physics and whimsy to guide you along. They are very rarely irritating, the main frustration coming, as with braid, from execution. While executing the solution is usually not hard, after playing braid with its ability to rewind it can be annoying to get quite far and realise you're not going to succeed and have to start again. The game does give time bugs that let you take back a few moves, but I'm not sure how much would be lost by providing the player with a near infinite supply of them rather than the handful you get.
Both games were a joy to play, but if you were to pick just one, I'd go for World of Goo