Included with Cubase 6.5 and now available on its own, Retrologue is a virtual analogue synth that holds no major surprises but sounds superb.
Two oscillators (with up to eight unison voices each, PWM, hard sync and cross-modulation options), plus noise and a sub, feed into a 12-mode resonant filter with onboard distortion, while two envelopes and a pair of LFOs shake the basic sound up, and delay and chorus/flanger effects bring some polish.
It's nothing particularly fancy, but clever touches like the fractional unison voice implementation, 'via' modifiers in the mod matrix and VST3 Note Expression make Retrologue deep and functionally comprehensive.
As we said, it sounds incredible - every bit as good as many synths costing three times as much. Basses bounce, leads scream and pads scintillate.
It's equally at home with modern urban/dance styles and more delicate electronic/hybrid material. A bit of onboard sequencing or arpeggiation wouldn't hurt, but you can't have everything for 40 quid.