VPN connections may easily be established between an Android device and pfSense in multiple ways.
This is a summary of the following information only. Please keep reading for more details!
|↓||(All)||CHAP||PAP||PSK||IPSec-PSK||IPSec-RSA||Xauth PSK||Xauth RSA||Hybrid RSA||Native||3rd-party App|
|2.1 (Eclair)||Yes (no encryption)||Probably||Probably||?||?||?||?||?||?||n/a||Maybe|
|2.3 (Gingerbread)||Yes||Probably||Probably||?||?||?||Yes (see text for details)||?||?||n/a||Maybe|
|4.0 (Ice Cream Sandwich)||Yes||Probably||Probably||?||Probably||?||Probably||?||?||n/a||Yes|
|4.1 (Jelly Bean)||Yes||Yes||Yes||?||Yes||?||Yes||?||?||n/a||Yes|
|4.2 (Jelly Bean)||Probably||Probably||Probably||?||Probably||?||Probably||?||?||n/a||Yes|
|4.2.2 (Jelly Bean)||Probably||Probably||Probably||?||Probably||?||Yes||?||?||n/a||Yes|
|4.3 (Jelly Bean)||Probably||Probably||Probably||?||Probably||?||Yes||?||?||n/a||Yes|
| PPTP is no longer considered a secure VPN technology because it relies upon MS-CHAPv2 which has been compromised. If you continue to use PPTP be aware that intercepted traffic can be decrypted by a third party, so it should be considered unencrypted. We advise migrating to another VPN type such as OpenVPN or IPsec.
More information on this can be found at https://isc.sans.edu/diary/End+of+Days+for+MS-CHAPv2/13807 and https://www.cloudcracker.com/blog/2012/07/29/cracking-ms-chap-v2/
See this note on Android and PPTP from a user on the forum:
For some devices, Gingerbread brought with it the "Advanced IPsec VPN" choices that will let it work with 2.0 and most likely other scenarios as well. Specifically these options are found on at least the Motorola Droid X, and likely others.
The VPN choices on these versions are:
The choices that use main mode (anything that isn't labeled "aggressive") likely won't work as the IP of the phone is used as the identifier, no matter what is entered in the phone's GUI, so it would require anonymous PSKs which are only available on pfSense 2.2 and later. Some Android IPsec GUIs may have an option to manually set an identifier. If that is present, it can work.
PSK v1 (AES, xauth, aggressive) works against a 2.0 server when properly configured. This combination is reported to work well - see IPsec Road Warrior/Mobile Client How-To for configuration details.
If another mode works that is not listed, let us know. The certificate method (Cert v1 (AES, aggressive)) should work in theory but has not yet been tested.
With ICS, the VPN options have been revamped and the following choices are available:
Of those, at least the IPsec Xauth PSK option should work, but testing is needed to confirm.
Should be identical to 4.0. One report so far of a working configuration with XAuth: 
Should be identical to 4.1.
Should be identical to 4.2. One report so far of a working configuration with XAuth: 
Should be identical to 4.2.x. One report so far of a working configuration with XAuth: 
Should be identical to 4.3.
Full results pending, but OpenVPN and IPsec in PSK mode work fine. PPTP connects OK. Needs further testing (Or not, PPTP should be avoided.)
Android 2.1 - 3.2: The FEAT VPN client, claims to not require root access and to work on older versions of Android.
Android 4.0 introduces a VPN API, so there are quite a few more third-party clients available.
Android 4.4 (KitKat) removed the "tun" device (/dev/tun); this change is reported to break most, if not all, of the OpenVPN clients, but has since been worked around.
The FEAT VPN client has been tested and shown towork on an Asus Transformer Prime and a Motorola Droid Razr, both with Android 4.0.x.
Stefan Baur confirms that the FEAT client works on his Motorola Milestone 2 (aka European/GSM "Droid 2"), and that none of the clients he tested work under Android v4.4 (KitKat).
With the latest update to the pfSense OpenVPN Client Export package, an "Inline Configuration" can be exported that has the config, the certs, keys, etc, in a single file. This file imports into the client linked above quite easily, as follows:
NOTE: When using K9 mail, and possibly others, when the attachment is saved to /mnt/sdcard/ the OpenVPN app will launch and import automatically.
Now that it's saved, the username must be set if User Auth is configured on the VPN server.
The VPN should now connect.
After the VPN has been successfully configured and tested, remember to remove the .ovpn file from the SD card in the Android device. The settings are stored securely by the app, so keeping the file on insecure storage is not needed nor recommended.
L2TP/IPsec in PSK mode has been proven to work at least on Android 4.1.x. For instructions, see L2TP/IPsec on Android