Costigan rhymes with:
colligan, donegan, dunegan, dunigan, finegan, hourigan, jarnigan, jernigan, branagan, burgan, colligan, donegan, dunegan, dunigan, dunnagan, finegan, hannagan, hourigan, jarnigan, jernigan, lanagan
Costigan sounds like:
cadogan, castagna, castagno, catchacan, catechism, cetacean, chautauquan, citizen, cotugno, cutchin, cutugno, cytogen