When you're looking for a bit of that vintage feel, Ladder Filter will twist your basses into squelching retro-licks akin to those of the Moog or the 303. Crank the drive up an extra notch and it will even function as a warm distortion. The Ladder Filter simulates low pass filters found in classic hardware synths:
Ladder Filter shines on it's own, but it was primarily created to power up the different "Snapin Hosts" Kilohearts offer. These are bigger effects units that utilize all the available snapins and give you a really fun and creative workflow for combining them in any way you can think of. So have a look at Snap Heap and Multipass right now.
Ladder Filter is also available as a Rack Extension for Reason over at the Propellerhead shop.