There's three that come to mind.
Gamecube - Metroid Prime (It'd been so long since the last Metroid game and I had to convince my parents.)
PlayStation 3 - Metal Gear Solid 4: Guns of the Patriots (Metal Gear! I picked a PS3 up as soon as I could once it dropped.)
Vita - Persona 4 Golden (I actually picked up P4G nearly a month before my Vita, but when I saw it sitting there so cheap I knew I needed to get a Vita.)
Thankfully I regretted none of these decisions.