In terms of the number of lines, Hamlet is the longest play in Shakespeare, and the title character the longest part. Of course, the fact fits in with one of its central themes: the relationship between words and deeds, and how they mix in human minds and lives. One great example occurs in 1.3. As Laertes is leaving to return to Paris, he says goodbye to Ophelia by warning her not to trust in Hamlet's romantic interest. The scene begins thus:

LAERTES

My necessaries are embark'd: farewell:

And, sister, as the winds give benefit

And convoy is assistant, do not sleep,

But let me hear from you.

OPHELIA

Do you doubt that?

LAERTES

For Hamlet and the trifling of his favour,

Hold it a fashion and a toy in blood,

A violet in the youth of primy nature,

Forward, not permanent, sweet, not lasting,

The perfume and suppliance of a minute; No more.

OPHELIA

No more but so?

He then goes on to explain that Hamlet, as a prince, can't entirely speak for himself, and if Ophelia gets fooled by his words that she will lose her reputation permanently. This takes him thirty-five lines. Her answer, one of the most wonderful moments in the play, tellingly, receives less than one line in response:

OPHELIA

I shall the effect of this good lesson keep,

As watchman to my heart. But, good my brother,

Do not, as some ungracious pastors do,

Show me the steep and thorny way to heaven;

Whiles, like a puff'd and reckless libertine,

Himself the primrose path of dalliance treads,

And recks not his own rede.

LAERTES

O, fear me not.

Here's a link to the scene (http://shakespeare.mit.edu/hamlet/hamlet.1.3.html).