I have to add one to the list:

An old geezer in the old folks home took a fancy to an old lady who is also staying at the home.
One day he gets enough courage to tell her he wants to make love to her.
She agrees that when everyone else is gone on a day trip, they will stay behind and get to it.
He goes to her room on the day and asks her how she likes it. She says,

"I used to like it when a man went down on me".

He says he would love to and goes for it. After about 30 seconds he comes back up and says,

"I'm sorry. I just can't go on. It smells rotten down there".

She says, "It must be my arthritis".

He looks at her and says, "Surely you can't get arthritis down there. Even if you could it wouldn't cause that horrible smell".

She says, "No, my arthritis is in my shoulder. I can't wipe my Ass".