What I already have:
Lehle 3@1
MXR M134 Chorus (OK, it's slightly wider than a boss unit, but it's still only one effect in a single pedal, so I'm counting it!)
MXR M117R Flanger (ditto)
Morley Bad Horsie (I guess that's bigger than a Vox too, but I don't think MOrley should be penalised for other people's cr@ppy designs ;))
(OK, my pedalboard also has a Lehle Looper & MXR Phase 90, but I hardly ever use those & could easily manage without them...)