Novation Bass Station II - Great monosynth for the money, can sound as good as something 5x more expensive.
Mutable Instruments Ambika - One of the most wonderful sounding synth I've ever played. Payed the same as on the BS2 in my local currency. Best deal I've ever made.
Korg Volca Sample - Cheap and very fun to use "does it all inside a tiny box" package.