1. Lots do. Search this forum for "companion fares" and you'll get lots of hits.

2. Be aware that the "get-one-free" ticket is only good if your "buy one" ticket is expensive, and that normally, you can buy two tickets for less than the price you will pay for the "buy one" ticket, so this offer is normally never used by those who receive it.

3. If you start a thread that asks a question, it is considerate to put a question mark in the thread title ("2 for 1 flights?" instead of "2 for 1 flights"). That way, everybody who sees it will not click onto it thinking that you have just discovered some exciting new offer that we should all be made aware of.