Had a tough time against a Space Marine list with my Orks the other day, and he didn't even have chapter tactics.
Mine was a hodepodge of the normal units that I just like to play:
1750 - 1 Battalion
Warboss w/PK and Kustom Shoota
Weirdboy w/Da Jump
30 boyz w/slugga (also nob w/PK)
20 boyz w/shootas (also 2 w/ Rokkits and nob w/Kustom Shoota)
10 Gretchin
Painboy w/Orderly
5 Nobz w/2 PKs and 3 Big Choppas
3 Meganobz w/1 Combi-Scorcha
10 Stormboyz (also Nob w/PK)
Dakkajet w/6 Supa Shootas
Def Dread w/1 Big Shoota and 1 Scorcha
Battlewagon w/Kannon and 4 Big Shootas
Mek Gun w/Kustom Mega-Kannon
2 Trukks w/Big Shootas and Wreckin' Balls
Shoota Boyz went in the Battlewagon
I don't remember exactly, but he had something like:
1750 - I think a Vanguard and a Battalion
Captain on Bike w/Power Fist
Librarian on Bike w/Power Sword and Strength of Heroes and Warp Time
Lieutenant w/Assault Bolter
5 Tac Marines w/Metlagun
5 Tac Marines w/Plasmagun
5 Tac Marines w/Grav Canon
?Sicarian? (I think that's what it's called)
Contemptor Dread w/Assault Cannon and Storm Bolter
5? man Bike Sqaud (I think, might have been 6) and w/Grav Gun and Sarge w/Power Axe
6 Devastators w/2 Las and 2 Missiles
Razorback w/Heavy Bolter
Razorback w/Assault Cannon
Rhino
Can't really speak for him but I think we both had a good time, but I can't help but wish my Boyz had performed a bit better. I was able to surprise him by jumping my 30 boyz unit into his backline and charging his Captain and Librarian but I wasn't able to get many attacks off and the Librarian lived on 1 wound with the Cap taking no damage. My Dakkajet was almost destroyed turn 1 and then took 3 wounds off of a Razorback before dying. All in all I had a hard time concentrating any force onto his side of the board while he was able to pick off my stuff one at a time. I was also rolling pretty poorly that game, but I don't want to that at fault for everything. I guess it didn't help that it was the Hammer and Anvil.