gift that keeps on giving

noun2

1. •
   Something with ongoing consequences; usually, one with positive ongoing consequences.

   • Those flower bulbs that our neighbor gave us are a gift that keeps on giving — they keep blooming year after year.
2. •
   (slang) A sexually transmitted disease.

   • That one-night stand that some tramp gave him is a gift that keeps on giving — he's had syphilis for years now.