I play mostly heavy metal and rock, so in actual fact, I barely use modulations or delay. Just drive and cleans for me. But of all effects available in the market, I like Chorus the most.
I don't know why, but I can't stand the sound of phasers, flangers (Ok la, I find some flange effect nice once in a while), reverb, etc. But I do like chorus, its quite nice and doesn't modify my tone too much unlike other effects.
I'd add a chorus to my rig actually, adds fatness and 'darkens' the tone for the gothic metal I sometimes play.