Here is a useful grass texture pack for games or any 3d app.

50 lossless 512×512 png are provided

1 blender file with a particle grass sample so you just have to tweak the particle settings to make your own 2d grass textures

The blender file also contains a low poly model to show you a good way to make your ingame grass, far better than the old traditionnal billboard plane (technique used in games like Oblivion)