I just finished readin Immortal Rain. Although I did like the story I've got to say there are a lot of similarities to Trigun for me. For instance the hero is somewhat tradegic and both loose someone they love. Both are manipulated and tortured by the antagonist to extreme measures. Did anyone else thins so.

Ahh, I really loved Immortal Rain and Trigun the anime (I haven't finished the manga yet).
Is Immortal Rain completed in Japan? I thought the author was not finished yet.
Now that you've said it, Immortal Rain and Trigun are similar in those aspects. Also that Rain and Vash are both tall, light-haired, and of gentle disposition, but can be very strong. Differences would be the story genre - Immortal Rain is shoujo, and Trigun sienen (or shounen?). There's much more development about Rain and Machika's relationship than I've noticed in any relationship in Trigun.