1. A damp squid. (Should be a damp squib. A firework. Let's face it, a squid is always going to be damp!)
2. Like a bowl in a China shop. (Instead of a bull in a china shop, which is much more likely to be a problem!)
3. For all intensive purposes. (Should be "For all intents and purposes" of course!)
4. Be more pacific. (Specific!)
5. I’m extremely high rate. (Irate!)
6. Going off on a tandem. (...at a tangent!)
7. Biting my time. (Biding!)
8. Playing Devil’s avocado. (My favourite! Devil's advocate, of course!)
9. We have to nip it in the butt. (Ouch! They mean bud!)
10. Trouble with his prostrate. (Prostate, as opposed to having trouble lying down!)

A few more: 

I’ve been passed from pillow to post.

It's just rubbing salt into the womb.

I'm on tender hooks.

I want some cold slaw on my salad.

I feel like a social leopard. 

Have you heard some you would like to let us know about?