The variants in pronunciation across the varying dialects have brought about some interesting lexical changes as well.

Since certain phonemes aren't pronounced in certain regions, the vocabulary has necessarily changed to reflect that. For example, (iirc) in Venice, the soft 'sh' sound is always hardened to 'sh'. In the rest of Italy, the words for "fish" and "peach" are really only differentiable in the plural, pesce(pes-shay) and pesche(pes-kay), respectively. Since there is no phonetic difference in the Venetian pronunciation of the two words, they have a different word for "peach"* (since Venice is a coastal town, fishing is more important and was probably more of a trade commodity, hence the choice).

Italian slang is also influenced by dialect. The pronoun 'ne', meaning 'some of that' in Standard Italian, has been expanded to also mean there in Florentine slang, hence the term "Amone", a shortened form of Andiamone, let's go there.

Italians will also occasionally switch to dialect to confuse outsiders who understand Standard Italian; the variations in pronuncian are usually enough to throw off the casual listener (or eavesdropper).

* which i can't remember!

i'll be updating this as i get better examples. stay tuned.