[quote=BrobyDDark]
There aren't any Trigun references in Gungrave, as far as I know. Didn't read the manga. Only watched the show.
[/quote]

From what I understand Gungrave happens many many many years before Trigun, but on the same world. The only direct nod that I remember is the weird animal thingies that they use as horses in Trigun appear in Gungrave for a race.