Medicine

The two syllable med'sun is pretty much confined to the UK and isn't particularly common even there. Dying out in favour of pronunciation driven by orthography? Will med'sun soon seem as archaic as sowjer?

Schedule

It appears that the long standing American myth that Canadians say shedule is false. That is the dominant, but by no means universal, British pronunciation. Canadians, like Americans, say skedule.

Slough

There seems to be a strongly held view that the pronunciation depends on whether one is shedding skin, sluff, in a bog, slow or slew, or preparing to bomb a railway town, slow. No obvious regional patterns are apparent.

Waistcoat

Weskit is a minority usage but it doesn't correlate with med'sun and it's distribution appears to be random. The usage is attested from Paris to Seattle.

Tomato

Predictably Brits and Antipodeans say tom-ah-toe or tom-ah-ter while North Americans say tom-ay-toe.

Subsidence

This one seems to be entirely random.