Soundfont Player with 4 Envelopes
The KX SF2-ST plugin by Xavier Kalensky is a great freeware stereo soundfont player. The VST plugin features 4 ADSR envelopes and an LFO to modulate the amplitude, frequency cutoff, resonance, and pitch. KX SF2-ST is capable of some serious modulation (listen here
for an extreme example), but at the same time it is very easy to use.