If you're looking for some serious bang for your buck, it's hard to go wrong with KV331's excellent Synthmaster. Essentially a synth Swiss Army knife, Synthmaster is a massively detailed semi-modular synth that allows Virtual Analog, Additive, Sample Playback, Vector, Wavetable and more sounds to be programmed with a great deal of depth. A lot of care obviously went into the design of this synth as they seemingly have thought of everything. A synth-programmer's synth. And did I mention is sounds amazing, too?
7. Madrona Labs Aalto ($99) [Read the Waveformless Review]
This one is definitely not for everyone, but those of you knob-twiddlers out there who love getting lost inside a Buchla-like modular synth unlike anything else you've used will find a lot to love here. It is based around what is essentially a 2-oscillator FM set-up fed through a Waveguide/Delay and Multimode Filter (based on the Oberheim SEM) into a nicely old-school sounding Reverb. Two envelopes, and LFO, a Sequencer and other modulators can be routed just about anywhere for all sorts of modular insanity. If you're looking for trance leads, move along, but if you love weird, unpredictable synths, don't miss this one!
8. Plogue Chipsounds ($95) [Read the Waveformless Review]
If the 8-bit sounds of yesteryear are your thing, you absolutely have to check out Plogue's Chipsounds. This synth emulates 15 different 8-bit sound chips from popular home computers, home video game consoles, and arcade games and lets you use them to sculpt your own new sounds. You can mix and match up to 8 different layers, each with their own type of chip, if you so desire, so the ability to make thick sounds out of traditionally thin-sounding oscillators opens up. It sounds amazingly authentic and is tons of fun to play around with, especially if you're a fan of unusual sounds.
9. Sonic Academy A.N.A. (£49)
Here's one that has slipped through a lot of people's radar. Sonic Academy is a website that musicians can subscribe to in order to access a generous and ever-expanding selection of video tutorials covering different aspects and tools of various electronic music genres. However, they also created their own software synth. A.N.A. (short for Analog Noise Attack) combines 3 virtual analog oscillators, 2 "noise "oscillators" that play back a variety of different inharmonic samples, and a 6th "attack" oscillator which plays back sampled attack transients. If that sounds a little bit like an updated version of 80's synths like the Ensoniq SQ-80 or Roland D-50, thats because the concept isn't that far off. A.N.A. brings that synthesis concept and gives it more flexibility and improved sound quality and marries it with some excellent presets in the house/techno/trance/EDM style. And as if the price wasn't already cheap enough, if you are already a subscriber to Sonic Academy, you can pick it up for only £29.
10. Sonic Charge Microtonic ($99)
Now in its 3rd version, Sonic Charge's Microtonic is a fantastic little analog-style drum box. Use the oscillator, noise, and filter to build a kit of up to 8 different sounds and program your own vintage-sounding beats with the built-in step sequencer. While the sounds it produces are generally unapologetically old-school, by layering several sounds at once, more complex and modern drum sounds become possible. And in one of the coolest innovations I've seen in awhile, Sonic Charge created the Sonic Charge Patternarium which generates new, "genetically mutated" patterns based on user feedback. Hear a beat you like? Simply download the preset and load it right into Microtonic!