Double-Sided Pedal Wrench - 1610/2
Product No. 615011$14.99 $11.25
These pedal wrenches are known and loved by people that have been in the bike game for a while and for good reason. It's made of drop forged, heat treated steel, is low profile to fit the thinnest of wrench flats, and best of all, it's beyond inexpensive for the quality you're getting.
The wrench is 5mm thick, 340mm long to give you all the strength and torque you'll need for even the most stuck pedals.