Funny wedding speeches are very important if you want to make the audience laugh and to remember this moment that you have waited your entire life. You must consider the fact that a lot a lot of speeches have been ruined by bad jokes, so think carefully when doing one. Here's an example on how not to start your wedding speech:"Adolf Hitler once said...".
So what do we have to do to create funny wedding speeches? Firstly, you have to understand your audience. If your audience is intimate as in only close family members and friends you will know already what type of people they are and how they will understand a certain type of humour. Reflect the humour in certain situations and not on people as this can make them feel unconfortable about something embarrasing that happened to them. But if you carefully plan your words you can use some mother-in-law jokes, blonde jokes or priest jokes for instance.
Also, self-deprecating jokes prooved to be very successful at weddings.
Here's a nice example of self-deprecating humour:"When I was younger, the neighbour's kid was terrified of me.One day I got close to the child and whispered to him: Don't be scared, little boy! I don't eat children...on Sundays!".
In-jokes are recommended for wedding speeches but only if both families have a long history together as they are familiarized with each other.
Playing with words doesn't always work in certain scenarios especially when in the audience there are people that speak a different language than the others. They could be funny to someone else but in these situations not everyone will enjoy them. Consider this aspect if there are too many non-english speakers, for instance, in the audience.
To finish, I hope this is some valuable info for you so I wish you the best of luck in choosing the right funny lines for your dream-wedding.