I'll second Black Lagoon. The action gets a bit over the top and silly sometimes, but it's not something to take too seriously anyways. Overall a very easy show to get into and the quality is really high.
I also see you like Trigun a lot, but don't have Gungrave on your list. Gungrave is overall more of a completely package than Trigun since it actually ends and was more emotional in my opinion (being more serious), and there's tons of action with it's mafia/gang wars elements. It was directed by the same person who did Trigun if I'm correct, well I know there's some connections here. So chances are you'd really like Gungrave being a bit Trigun fan.
If you want a good dark and twisted anime Texhnolyze is awesome. The setup is kind of like Gungrave's, gang wars and all that, while there's some slow odd mind thriller parts to the show, there's actually quite a lot of action too. Very dark and hard to get into though, for some.
If you want some cool more realalistic fights (i.e. no special fireballs or powerups, that kinda stuff) then try baki the grappler
you see some interesting fights if you get deep into it, like sumo vs pro wrestling, street brawling vs karate... some real interesting match ups... just one thing, the anime art takes a bit to get used to but trust me, well worth the effort if your up for some nice real fighting anime
D. Gray Man is the most horribly paced anime. I would not recommend it if you are looking to get as much action as you can right away.
Tenjou Tenge, Scrapped Princess, and Fate/Stay Night would be the three that I would recommend most not already on your list. Tenjou Tenge is pretty exclusively about fighting, Scrapped Princess has more of a plot emphasis, and Fate/Stay Night is mostly fighting but also too romantically cheesy.
I would recommend Berserk, but if you are trying to watch a lot of stuff, it is not worth it to get caught up in only to find out you have like 200 more chapters of manga past where the anime stops to traipse through.
Elsewhere, a somewhat startled Warren Worthington III finds that he has accidentally wandered into an electrified east-side world of post-twist teens and watsui-ing teeny-boppers...
im also lookin around for an anime with a lot of action scenes in it i've seen every thing mention'd in this thread thus far and many more if you take a peek at my list it needs a pretty large update i've seen way more than the 500 writen down there. I should really update that list but ill do that another time.
if any of you have a recomendation let me know "just no mech anime just got done with a binge on that genre"
profile comments or messeges are fine you dont have to reply on this thread if this thread is even active any more