Chancer

n.

Heard in Dublin, Wicklow, Kilkenny, Galway, Longford, Kildare and Limerick

An opportunist, a scammer! I think it comes from "Chancing his arm", like "trying his luck"!

In use

He was trying to charge me EUR 10 instead of EUR 5, the chancer!

Posh English

He attempted to relieve me of ten euros instead of five, the opportunistic scoundrel.

Same phrase, other counties