Use it for the bottom of an aquarium. 55x30 would be a really nice deep tank. Or there might be a DIYer out there looking for a cheap foundation for their tank. I'd think about taking it off your hands if I was anywhere near your neighborhood.
Or break it which is lots of fun too
55x30 sounds like a dream tank!! Seriously. I'm not sure if I would use the piece as it is though with the holes (true they could easily be covered by a small piece of glass and some silicone) and most notably the score line... I'm not sure how that would affect the tempered glass's strength or it's probability for failure.
I'm excited to break some sh!t.