The funniest speeches often have two speakers. I have seen friends dressing like the couple and putting on little shows. This is really fun if you are good at mimicking and really know the couple. To guarantee humour have the bestman play the bride and the maid of honour could be the groom.
By writing a cheesy poem which rhymes and is completely individual, you can grant yourself permission to read and be cheesy. People want to laugh at a wedding. They don’t want you to experience an award silence. You would have to be awful for them not to laugh. So as long as you make it about the couple and from the heart they will laugh at a corny poem. I promise.