One that I like, but is probably rather old-fashioned, is 'Wild horses couldn't drag me/make me...'. If the propsed action involves handling, 'I wouldn't touch it with a barge-pole'. If the other person proposes that s/he will do something you don't want, s/he'll 'do it over my dead body'.
More generally you could say 'I wouldn't do that if you paid me/for all the <valuable thing>' - for example 'I wouldn't do that for all the money in the world'. A well-worn one (rather clichéd) is '...for all the tea in China'.
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