mine would have been my boss Mega distortion that i enjoy but that led to a addiction... a pedal addiciton hahah!
First off, I started with an Ibanez Soundtank Chorus pedal, I was charged about $100 for it and it was used (which was probably a ripoff), but in all honesty it was a great pedal, the only problem was that I usaully never use the chorus effect. My second pedal was a wah-wah that never really worked properly, it would give me a slight wah effect on the lowest string on some of the low frets but for everything else it was almost useless. From there I got a Dunlop Crybaby Wah-wah that I love, after that I got a Ibanez TS-5 tubescreamer and a few Danelectro pedals that I traded in for a Digitech RP-80.
Right now I have the RP-80, the Crybaby and a Danelectro PB and J Delay pedal, which are all good effects. The main problem i've had is that the crybaby and danelectro don't work well with the RP-80 for some reason. The RP-80 is a good tool but I think I'd rather go out and get a nice Fender tube or a Marshall tube, depending on whether or not I want to buy a distortion pedal or use an amp with a good distortion and mediocre clean sound.
The moral of the story is that I've been playing for almost 7 years, and I still have no concept of good guitar tone.
Steve-0