I used to be a full-on "Boss guy" dreaming of full pedal boards of only Boss. I figured that "just Boss" would keep everything neat and clean. I ended up coming to the conclusion fairly early on that too many Boss pedals in your chain (or just the CS-3 and something else) sounds like ASS. I'm old enough to be an original buyer of a few MIJ Boss pedals. I like some Boss pedals for what they can do, but a good number of Boss pedals I got in my early days were real stinkers.
I was an original buyer of a Boss HM-2. I loved it until I played it in a band situation. After trying to make it work a few times and failing, I decided it had to go. I probably shouldn't have gotten rid of it because in retrospect, I think it's cool for practicing, but I have never found another pedal that, in a band situation, made my playing so completely disappear with everyone else playing. It was as if clicking on the pedal was like this amazing mute button. How anyone can use that pedal today and "cut through" is beyond me. Given that weakness alone, I can't understand the current fanboyism surrounding it.
Here's what I had that I ended up getting rid of:
HM-2: Explained
CS-3: Too noisy
SD-1: Meh. Seemed nowhere as cool as an actual tube screamer.
OD-2: Turbo Overdrive. Not metal enough.
DS-2: Turbo Distortion. Not metal enough. Couldn't get a good sound out of it.
DD-3: MIJ. Gave it away to a friend.
HF-2: Hi-Band Flanger MIJ. Sales d00d @ Guitar Center said it flanged just like the BF-2. He lied. I think this pedal is just about worthless for guitar. Perhaps other instruments can make use of it, but I found it to be possibly the most uninspiring pedal I've ever used.
GE-7: The stupid rubber tips that would so easily fall off the sliders pissed me off. I thought it was too noisy as well.
PH-2: I thought this was about as lame a phaser sound as was possible.
Boss I currently have:
DD-3: MIJ. I somehow happened upon a situaton where I owned 2. I still own one.
DD-20: I think this is a good pedal
OC-2: Fun. Too bad it's not polyphonic.
RC-2: I like fooling myself into believing I'm "learning" how to use it, but it's not been out of its box in well over a year.
XT-2: Not for everyone, but I actually think it's one of their better "old" distortion pedals. I like that only 20,000 were made and IMHO, it does quite a good job at passable Sabbath tones.
DN-2: Dyna Drive. I got this for $40.00 on eBay last week. I am aware it employs that crap Boss COSM tech, but it also seems like it might be good for pushing the front of an amp. I've yet to try it.
BD-2: Thought it sounded pretty good. I think I got it for $55. Tone knob has to be rolled all the way off or it's ice-pick city. Pedal has been in pieces for over a year waiting for me to apply a Monte Allums BD-2 kit I bought to mod it.
CE-5: I don't know why I bought this. I don't particularly care for Chorus sounds. However, I did make a point of buying the older analog version to try out some "cut this capacitor and it will sound better" mod. I'd probably be better off just selling it back on eBay.
Boss I actually plan on acquiring:
PS-6 Harmonizer. Oh to be able to play BOTH guitar parts of "The Boys are Back In Town".
RE-20 Space Echo. Just 'cause
TU-3 Tuner. I have a Peterson StroboStomp 2 tuner, but I think I'd rather leave that at home for tuning and set-ups than to keep it on a pedalboard so someone else can steal it.
I also have some EHX and a few b00tEEk pedals (probably about 50 pedals total), but I've come to the conclusion that insofar as "big" pedalmakers are concerned, I'm mostly in the Dunlop/MXR camp. Despite all my griping about Boss distortion/overdrive, I actually think they tend do a better job on distortion than Dunlop/MXR. At the end of the day, I've found that I prefer boosts and amp distortion. I think Dunlop/MXR does a much better job of good modulation pedals than Boss. The MXR 117-R Flanger was exactly the sound I wanted.
i forgot to mention it in my List 
because they're AWESOME