Best Bang-for-Buck Power Mods?

Alright, so I’m always trying to squeeze a bit more out of my ride without completely emptying the wallet. I know the basics like a good tune or an intake, but I’m curious what you all have found gives the biggest horsepower bump for the least cash. Are we talking exhaust work, a smaller pulley, or something else entirely? What’s been your most cost-effective mod that actually made a noticeable difference on the dyno or the street?