.gitignore for Unity3D projects. Source: https://stackoverflow.com/questions/21573405/how-to-prepare-a-unity-project-for-git/21573406#21573406

.gitignore

### You need to do this first:
# 1 .Enable External option in Unity → Preferences → Packages → Repository (only if Unity ver < 4.5)
# 2. Switch to Visible Meta Files in Edit → Project Settings → Editor → Version Control Mode
# 3. Switch to Force Text in Edit → Project Settings → Editor → Asset Serialization Mode
# 4. Save Scene and Project from File menu.
# 5. Quit Unity and then you can delete the Library and Temp directory in the project directory. You can delete everything but keep the Assets and ProjectSettings directory.




# ========================================================================= #
# Builds folder (rename this to whatever folder you create for your builds) #
# ========================================================================= #

Builds/

# =============== #
# Unity generated #
# =============== #
Temp/
Obj/
UnityGenerated/
Library/
Assets/AssetStoreTools*

# ===================================== #
# Visual Studio / MonoDevelop generated #
# ===================================== #
ExportedObj/
*.svd
*.userprefs
*.csproj
*.pidb
*.suo
*.sln
*.user
*.unityproj
*.booproj

# ============ #
# OS generated #
# ============ #
.DS_Store
.DS_Store?
._*
.Spotlight-V100
.Trashes
Icon?
ehthumbs.db
Thumbs.db