I've tried numerous products, including meguiar's, but this is the only metal polish I've used that actually does what it claims to do. T-Cut original Metal polish. I thought I'd post up on here as I'm sure I'm not the only one that has spent lots of money on products that aren't much cop.
Here's a photo of my exhaust, which has been on for years, polished up using T-Cut. It even got the inside of the pipe shiney! Not that it will stay that way mind
And for those who like photos:
Product image for ref
http://www.carandcamping.co.uk/shop/images/uploads/METALPOLISH-TMP100.jpg