TriScan

TriScan (トライスキャン) is a triangular program that appears in Cyber Peacock's stage in Mega Man X4. It will home towards X or Zero and deal contact damage. If it's not destroyed after a while, it will leave the screen. 

TriScan Gold
TriScan Gold (トライスキャンゴールド) is a slightly modified TriScan that appears in the last Sigma stage of Mega Man X5.

Other Media
TriScans appear alongside Hover Gunners and Spike Marls in the Rockman X (manga) fighting Zero, but get destoryed by him.