I just went to their site and listened, to some of the demo sounds, made in massive. Most of those cool sounds, can be made, with some of lmms's internal plugins, like Triple Oscillator, and moreso with the monster plugin, called ZynAddSubFX.
The chiptune sounds and bass sounds, can be made with sfxr, nescaline, free boy etc.
These free 3rd party vst's below, can make alot of incredible sounds too:
Synth 1
T-Force Alpha Plus
Oatmeal
DSK OranZe
And there are lots more.