No More Heroes 2: Desperate Struggle. Bought it full price, beat it just over a day later, was kinda like "Yeah, I should wait for most games to go on sale."
Also part of the reason I love achievements so much is because even games like that will have some artificial replay value because of it.
A console I maybe regret is the sticking with the Gamecube over the PS2, but then again almost everything on the PS2 has been re-released with achievements on later consoles.
Wii U's looking like a bust atm too since almost everything's been re-released on the Switch. Just Mario 3D World, the first Splatoon, and Xenoblade X (which froze on me and doesn't have auto-save, so I'm too spooked to play it) out of what I played is still exclusive.