I have an early Klon, and the great thing about them is that they are very transparent sounding. They add just the right amount of edge and drive without affecting the tone of the guitar. I had avoided this thread because I might actually have a lot of the pedals that people are listing (I have an original MXR phase 90 (and phase 100), original JEN Cry Baby, original tone bender, hot cake, v-twin, etc). But since I am now replying, these are my top 5
Original Watkins Tube Copycat
Boss CE-1 Chorus
Foxx Tone machine
WEM Wah Wah
MXR Blue Box
I admit the copycat isn't a pedal, but I used to have one that had been modified to include an extra playback head and the sound was great into a Selmer T&B 50. The WEM wah was unusual in that there was no on-off switch, so it is always in the signal path. I should never have got rid of mine!!