Doomtrain
How to obtain
Now Doomtrain is a little harder to obtain than your average GF.  In disc 3 you need to have 6 marboro tentacles, 6 steel pipes, 6 remedy+, and the solomon ring.  Once you have all these items use the solomon ring and Doomtrain will join you.  You might wander how people know this but its quite simple.  Just collect and read all the Occult fan magazines. 
Description
The enemies appear on a stary background like the one on this page.  And under them form train tracks.  From far away the Doomtrain starts its yourney towards his enemies, then he smashes into them.  When the enemies fall they take little damage but they will have a few status changes like blind poison meltdown silence and so on.
Iggy's opinion
This has got to be the most handiest GF in the whole FF universe.  Shure it does little damage but the status effects come in very handy especially agains bosses.  Not to mention the Call Junk Shop ability which allows you to call a junk shop from anywhere.
9/10.
Ability
Ability                  AP        Description
Elem-Atk-J
ST-Atk-J
Elem-Def-J x4
ST-Def-J x4
Magic
Draw
GF
Item
Darkside
Absorb
Auto-Shell
SumMag+10%
SumMag+20%
SumMag+30%
SumMag+40%
GFHP+10%
GFHP+20%
GFHP+30%
GFHP+40%
Boost
Junk Shop
Forbid Med-RF
Learned
Learned
180
180
Learned
Learned
Learned
Learned
100
80
250
40
70
140
200
40
70
140
200
10
Learned
200
Junctions magic to Elem-Atk
Junctions magic to ST-Atk
Junctions 4 magic to Elem-Atk
Junctions 4 magic to ST-Def
Use Magic command
Use Draw command
Use GF command
Use Item command
Use Darkside command
Use Absorb command
Automatically puts character on shell
Raises SumMag up by 10%
Raises SumMag up by 20%
Raises SumMag up by 30%
Raises SumMag up by 40%
Raises GF's HP up by 10%
Raises GF's HP up by 20%
Raises GF's HP up by 30%
Raises GF's HP up by 40%
Boost your GF
Call Junk Shop from inventory
Refine forbiden medicine from an item
1