I'm not familiar with Melty Blood, but I assume this is some sort of giant vampire-hunting stakegun. "Melty Blood Re.Act 1/7 Scale Pre-Painted PVC Figure: Ciel (Clerical Garment Version)" is $100 at Play-Asia.
I did dig up a video compilation of massive combos in the Melty Blood 2D fighter (no giant guns during the portion I saw):
*Previously: Vampire lusts for plush animals.
*Buy Melty Blood toys at eBay.