The ZGMF-X56S/θ Destiny Impulse is a prototype integrated weapon system mobile suit, it is featured in SEED DESTINY-MSV. The unit is piloted by Courtney Heironimus and Mare Strode.
Here's a professional kit bash by Bandai Hobby modeler. The modeler used MG 1/100 Sword Impulse Gundam and MG 1/100 Destiny Gundam to make the variation Destiny Impulse Unit 3.
see more info at Gundam Wikia