 If you liked
Trigun
|
 ...then you might like
Et Cetera
|
This also applies to Trigun Maximum
A happy-go-lucky type main character with a gun, have amazing power by either by the gun or by themselves, set in a western-like environment.
A "priest" with questionable background and motives , Morality conflict among some of the characters at times (though Trigun is much darker and mature), traveling the wasteland to achieve some kind of goal.
Though they are very different in terms of story/goal, you can get the same atmosphere and feeling from both of these manga.