Regigigas can eat Luxchomp for breakfast. (I should know; I have a Gigas build with a great track record...)
However, since there is so much Luxchomp in my area, there is just as much Vilegar and other Vileplume/SP locks decks running around. Since a lot of them run Mightyena LA, it can give SPs a lot of grief. (It annoys my Gigas as well, but it's nothing to lose sleep over...)
I wonder if I should enter Cities with Gigas, just to see how much mayhem I could cause... *shameless pitch*