frankly speaking I think I had at somepoint in time almost all the boss pedals there is available in the market today, either Id tweaked mod them then resell it again.
but for all times sake the best pedal I like in boss are the ff:
CE-5 moded (change one cap. only made a huge analog feel)
FZ-5 Fuzz
DD-3
OS-2
SD-1 is good but I sold it again anyway, but there is a clone made by denio sd-10 patterned to the sd-1, compared it side by side, And I must say the denio sounds fuller...just my opinion, still I own it and is a keeper though its cheap
BD-2 is good also but sold it for the same reason I have for the sd-1, theres something missing in its tone, same with the DS-1, DS-2 is almost good but too harsh so is the MT-2, TR-2 can be good after a 1 cap tone mod change...but as you go along you don't really need a tremolo since you have the trem bar.haha, I could go on reviewing each pedal but to keep it short
the OS-2 is a real gem so is the FZ-5 for their drive pedals
For all boss pedals lovers
I would say that modding their pedal really makes the sound different but still the best tone still is at their stock state.