Carl Martin 3-Band Parametric EQ/Pre-amp  

I was lucky enough to score a great deal on one of these pedals on an auction site and it is a fantastic tool.  On my Taylor acoustic I preferred the DI section on the Carl Martin to a Radial JDI.  The EQ is also perfect for guitar.  It has exactly the right bandwidth to always seem to hit where you need it to when cutting a resonant frequency or giving a little mid push in the perfect spot.  It also works great with my acoustic for pulling out some of the "quack" that comes from an acoustic pickup.  I would definitely recommend giving this a try if you can benefit from the DI as well as the EQ section.