Here is the list:

1 Unique Variant:
Autogun ASI MEDIUM - 300 CE
Autogun DMG Bonus VS Construct HIGH - 100
Autogun DMG Bonus VS Slime MEDIUM - 75
Autogun DMG Bonus VS Undead LOW - 50
Autogun DMG Bonus VS Beast LOW - 50

2 Unique Variants:
Autogun DMG Bonus VS Gremlin LOW - 100
DMG Bonus VS Slime MEDIUM