So far all mine are keepers as I don't know what it feels like to sell a game. Seeing all the nibs maybe I should consider moving on a couple but which ones 

I might wait until I see an absolute must have new release, Metallica nearly got me thinking hard.

I really love the early 80's Bally machines and system 1 Gottliebs but after playing Peter (Gorgar's) Metallica, I too think a Metallica would fit nicely amounst my collection. Fantastic fun game. I couldn't get enough if the Sparky multiball and the inline drop targets are awesome.