You're not exactly short of options if you want an affordable hardware synth, but Tasty Chips Electronics' Saw Bench still catches the eye thanks to its 100% analogue signal path and $100 price.
This single oscillator instrument sports a four-pole diode ladder filter, frequency modulation, two separate ADSR envelopes for the VCA and VCF and an LFO. It can respond to MIDI control and comes with six knobs, two buttons and two toggle switches (four of the knobs can be switched to control one of three different parameters at a time).
Currently the subject of a Kickstarter campaign, $60 will get you a barebones Saw Bench, $80 will get you a DIY model with a case, and $100 will get you the fully-built synth.
(Via Create Digital Music)