Meijer for me, but that's largely b/c I work there...
also if you use your meijer CC, you instantly get $.10/gal off the pump price.
if i'm outside meijer territory, whatever's cheaper, and on my route.
my most recent trip was to Fort Sill, OK taking my buddy to his brother's graduation from basic training.
once we were outside of Meijer Territory, it was Flying J, Kum and Go, Love's, and one of the stations on base.