This post is to clear up any uncertainties you may have about a device and it's potential for being unlocked. I'll go over each device in detail...

*iPhone 5...Well, there is no jailbreak, not yet anyways, so I really can't do much for you on this one!! SORRY!!!

*iPhone 4(s) ***AT&T***...If you are on iOS 6, then there is no jailbreak for you yet..sorry.
However, if you are on iOS 5.1.1, or 5.0, you are in luck. I can unlock (APN unlock, that is), for AT&T GoPhone, h2o, Red Pocket, Air Voice, Straight Talk, Net 10, and Jolt. No T-Mobile possibilities. That means Simple Mobile and Family Mobile are out of the equation, too, since they are T-Mobile shared partners.

*iPhone 4(s)***Verizon***...I can flash you to CricKet or Page Plus, Bad ESN or not, ONLY on iOS 5.1.1 or 5.0

*iPhone 4(s)***Sprint*** ....I can flash you to CricKet ONLY, and ONLY on iOS 5.1.1, or 5.0

*iPhone 4 ***AT&T*** ....Same story as the AT&T iPhone 4(s), except you CAN be jailbroken on iOS 6, but it is a TETHERED jailbreak

*iPhone 4***Verizon***....Same as iPhone 4(s)

*iPhone 4***Sprint*** ...Same as iPhone 4(s)

*iPhone 3G(s)....This is where it gets VERY confusing. Before anything, we need to identify which version of the 3G(s) you have. There are three different ones, all with different capabilities. You are going to be paying attention to the 3rd, 4th, and 5th digits of your SERIAL NUMBER. How you find that is Settings>General>About>Serial Number.
The 3rd digit is the year of manufacture, and the 4th and 5th are the week of manufacture.

Type #1-The most desired. 945 or earlier. You have a GEM!!!! You can be unlocked for ANY GSM carrier!!! So that is T-Mobile, Simple Mobile, Family Mobile, Straight Talk, Net 10, AT&T GoPhone, Red Pocket, h2o, Jolt, and Air Voice. Also, it will work for overseas GSM carriers!! AND>>>>you wil be UNTETHERED when jailbroken, no matter which version of iOS...even 6!!!

Type #2-134 or earlier. You can be unlocked for ANY GSM carrier (overseas included), BUT you will be TETHERED when jailbroken on iOS 6.

Type #3-135 or newer. You are limited to the same options as the AT&T iPhone 4.

The good news with the tethered jailbreaks on iOS 6, with a 3G(s), no matter which type, is that you can be downgraded to iOS 4.1, and have an UNTETHERED jailbreak!!!

*iPhone 3G...It is only capable of going as high as iOS 4.2.1, so no matter what, it is an UNTETHERED jailbreak. You can also be unlocked for any GSM carrier (overseas included).

*and finally...the old iPhone 2G. It is only capable of firmwares up to iOS 3.1.3, so it is also an UNTETHERED jailbreak, and can be unlocked for any GSM carrier (overseas included).

....I hope that this has answered any and all questions that you may have about unlock possibilities for your iPhone, if not, make sure to email me with your question!!!

                                                                                                       ~The iDevice Pro~