The hardest part of writing silly wedding vows is making your guests chuckle without making the vows trite, or promising things you can't (or won't) deliver. After all, promising to always put the toilet seat down might sound cute in the moment, but do you really want to have broken your wedding vow that easily? Instead, look for qualities about yourself that are funny or amusing, hobbies, or habits that can be incorporated into your vows.
Here are some examples of funny wedding vows:
I (Name), take you, (Name) to be my lawfully wedded (husband/wife) and chief tennis doubles partner, for richer, for poorer, for better, for worse, in sickness and in health, for when we win and the very very rare occasion when we lose. I promise to love, honor, and cherish you, to return your serves and do my best not to foot fault. This I vow to you.
I (name), take you (name), to be my beloved wife. I promise to love you and be your faithful partner, for better for worse, for richer, for poorer, when the Jets are winning, and when they are losing, in sickness, and in health, and in Jets-induced sickness. I will be true and loyal, and cherish you for all the days of our lives.
I, (name), take you (name), to be my (wife/husband), to have and to hold from this day forward, for better or for worse, for richer, for poorer, for even poorer when I've been shopping a lot, in sickness and in health, to love and to cherish; from this day forward until death do us part.
And of course, don't forget the Dr. Seuss funny wedding vows!