If a close friend who was seemingly straight came out as bisexual, and/or had a thing for you, how wuld you feel?

I would say, "That's cool, dude, pass the remote."

Most females are bisexual anyway

I would be happy for them and feel flattered.

It wouldn't bother me of course - if anything I'd be flattered. I'd let them down gently and make it clear that I value their friendship but that's all it is. If they kept making unwanted advances after that, that's when I'd start to get ticked off.

It could be tricky as I'd want to stay friends without hurting their feelings. Otherwise it wouldn't worry me.

As long as they understood the feeling wasn't mutual, if that was the case. Then no biggie.