1. Thor. Gets the bread and butter jobs done, and is useful for a whole lot of other non-synth jobs as well.
2. MClass Equalizer. It's the only EQ I really need, apart from the next device.
3.
Omega Trimmer (Forgotten Clank Studios). Gentle or very steep lowpass and highpass filtering and a +/- 30 dB gain in a compact 1U device. It's the perfect complement to the MClass EQ.
4.
Synapse DR-1 Deep Reverb (Synapse Audio Software). Creamy and lush reverb for occasions when none of the RV7000 offerings don't quite cut it.
5. The Echo. Basically the only delay device that I use for delay effects.
These are probably the ones that I use most often. There are a lot of other devices as well that almost made it to the top 5 (such as Selig Leveler and Spectral Scan Software 4 Phase LFO, and something as basic as the Audio Track if that counts). Without all these mentioned I would have to seriously rewire my brain to do a lot of the tasks.