Halo 3 Campaigns Complete: What hardness level did you do it in? what is your best level?

I have been playing Halo 3 on my Xbox 360 obviously when I can because of work commitments, but when I do get time I try and play it as much as I can. My cousin and I have been playing this game in campaign mode together online and must say have both been impressed by the graphics and game play.

To tell you the truth I have been playing this game on normal mode which really I should have chosen the hardest level as the normal is pretty easy. My cousin and I are already on MISSION 09: HALO; the game is brilliant but in normal mode is pretty easy if you ask me.

My favourite has to be Mission 07: The Covenant, just seems pretty cool when you fly the Hornet. A little bit disappointed that the game has nearly ended so quick but hey thank god for the multiplayer, I can play other people after. Will I be disappointed with the small maps in multiplayer mode thou, this is another question.

I love the Xbox 360 but for the sake of exclusive games for each console may consider buying the Sony PS3 as well, so many people going on about Warhawk which makes me want to play it.

Anyway back to the questions in hand: What hardness level did you do it in? What is your best level?