Aqualize:
I found this diode, what do you all think?
http://www.produktinfo.conrad.com/datenblaetter/150000-174999/160744-da-01-en-SCHOTTKY_DIODE_DSS25_0025B_TO_220_AC.pdf
(no, I won't forgetting cooling of it)
Measure the resistance of the motor windings with a multimeter and divide that into the supply voltage you will be using to get the stall current (Ohm's law). If it's less than 25A then that diode will be fine, with appropriate heatsinking if necessary. If it's a lot less than 25A, then a regular silicon power diode will be suitable and cost less. The only advantage of a Schottky diode in this application is that is has a lower voltage drop, so it dissipates less power and may not need quite as much cooling.