So, it all went back to Unity5 and how it integrates older plugins like Admob. Apparently, there is no ProxyActivity needed anymore for Android builds. So I completely removed the following out of the AndroidManifest.xml file:
<activity android:name="com.unity3d.player.UnityPlayerProxyActivity" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
<meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="true" />
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
And then moved the <intent-filter>
into the UnityPlayerActivity:
<activity android:name="com.unity3d.player.UnityPlayerActivity" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
Now Application.Quit() works no problem!
Complete AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:installLocation="preferExternal" package="com.example.admobtest" android:versionName="1.0" android:versionCode="1">
<supports-screens android:smallScreens="true" android:normalScreens="true" android:largeScreens="true" android:xlargeScreens="true" android:anyDensity="true" />
<!-- Mobile Ads Permissions -->
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<application android:icon="@drawable/app_icon" android:label="@string/app_name" android:debuggable="false">
<!-- meta-data tag for Google Play services -->
<meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version"/>
<activity android:name="com.unity3d.player.UnityPlayerActivity" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="com.unity3d.player.UnityPlayerNativeActivity" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
<meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="true" />
<meta-data android:name="android.app.lib_name" android:value="unity" />
</activity>
<activity android:name="com.unity3d.player.VideoPlayer" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
</activity>
<!-- Google Mobile Ads Activity -->
<activity android:name="com.google.android.gms.ads.AdActivity"
android:label="@string/app_name"
android:theme="@android:style/Theme.Translucent"
android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen">
</activity>
<!-- PurpleBrain AdBuddiz Activity -->
<activity android:name="com.purplebrain.adbuddiz.sdk.AdBuddizActivity"
android:label="@string/app_name"
android:theme="@android:style/Theme.Translucent">
</activity>
</application>
<uses-feature android:glEsVersion="0x00020000" />
<uses-sdk android:minSdkVersion="9" android:targetSdkVersion="19" />
</manifest>