For me, OTT is pretty well known.... but one that isn't used as much is the "Flatline" preset, I find this is great for tightening the low end and I often use the OTT and Flatline in combination (I play around with the wet setting on both).
I always add a channel with a a heavily detune saw with 100% wet reverb with a short tail. For me this add a huge special sound without a long messy tail (which losses the clarity of a song)
Its stupid but for me I often put a pitch shifter on my master bus when I am writing simply so I can get a completely new perspective on my compositions.