Originally posted by sbyrne due to an upcoming wedding (my son)
I hope you don't plan on being the photographer at that particular wedding
If you want to go cheap, the best solution is to find a used Pentax AF280T. Auto modes, very reliable, well designed, communicates with the camera.
If you want the cheapest PTTL, then a Sigma 500, 530 or 610 ST DG. No fancy modes, again reliable, a little more perks than the 280T. I just sold a 530 ST DG for 100$ roughly. New is more but affordable.
If you want the best bang for your buck, there are a few Pentax AF540FGZ currently on offerr in the marketplace. More expensive, more functions than you will ever use, but you will be able to grow into the flash and learn as you go.