You can charge with extra force.
Prerequisites: Medium or larger, Powerful Charge, base attack bonus +4.
Benefit: As Powerful Charge, but treat yourself as one size category larger than you are. For Colossal creatures, the extra 6d6 points of damage bonus becomes 8d6.
Special: A fighter can select Greater Powerful Charge as one of his fighter bonus feats.
Source: Miniatures Handbook, page 27.