So many, however those in recent memory include -
Diablo 3 - RIP Blizzard, no more sales from me.
ARMA 2 (bought for DayZ) - The shittiest engine in existence!
Red Orchestra 2 - But it's OK because I got a refund!
RIFT - WoW Clone #2,245, and WoW sucks.
Homefront - This was supposed to be my replacement for BF2 before BF3.
A.P.B. - Dead less than 3 months after arrival. Now F2P and brimming with cheats.
So much wasted money. Makes the blow sting all the more when you list them and realize. And that's not counting emotional damage from the hopes and dreams I had for them. 
I can never be free, because the shackles I wear can't be touched or be seen.
i9-9900k, MSI MPG-Z390 Gaming Pro Carbon, 32GB DDR4 @ 3000, eVGA GTX 1080 DT, Samsung 970 EVO Plus nVME 1TB