Dungeon Defenders. I figured it would be okay but nothing spectacular...turns out it was horribly addicting, remarkably fun, has tonnes of replay value, and above all else is REALLY fun to play with friends. In fact, it's really only awesome with friends, but when you have friends, it's epic.
Second favorite game of the year.
My Console Library:
PS5, Switch, XSX
PS4, PS3, PS2, PS1, WiiU, Wii, GCN, N64 SNES, XBO, 360
3DS, DS, GBA, Vita, PSP, Android