Welcome to Librarium Online!
I have recently read a number of posts about having DH's allied with Space Marines. I thought that DH's could only be used as Elite choices in a Space Marine Army, but now it looks otherwise and has got me interested!
I have the following models:
1 * GK Hero
1 * Inquisitor
1 * Vindicar Assassin
7 * GK Termiantors
7 * PAGK
7 * PAGK
5 * FAGK
How would you recommend alliying them with a Space Marine army and what would be the best configuration for them?
That also got me to thinking which would be the best Space Marine chapter to do this with?
many thanks for your help guys!
Warning: Long post ahead!
Unfortunately, there's no way to use that assassin with the models you have. This is because you need an Inquisitor to field the assassin, so the only way to include that Inquisitor (due to Elite slot limitations) is to make the Inquisitor an HQ choice Inquisitor Lord. And he is forced to take a retinue, which you don't have =(.
Besides that, it sorta depends what you want to do with them, what slots you have in your 'parent' list, how much you want to retain of your 'parent' list, and how much you want to spend on the Daemonhunters. But, four things come to mind:
1) HQ: Grand Master with Terminator Retinue (up to the 7 termies you have, though that's a substantial investment). 'Round here, we generally recommend around 4-5 Termies as a Retinue. As far as weaponry/wargear goes, try not to go over-board. The GM is already a deadly model. Often folks will give him a psycannon to capitalize on his excellent BS. Others will give him an Icon of the Just (gives him a slightly better Inv save). I don't like to do that, since it's a fair amount of points and a small improvement, but your call. I also personally like the Holocaust psychic power on the GM, since he's got the extra wounds to soak up any stray Perils attacks, and you can get sooooo very many hits with the power (which is in addition to his normal attacks in CC). You can deep-strike these guys if you so choose.
2) Elite: Terminators. This is similar to the above, but your squad leader is not an Independent Character, so he can't be singled out of melee. Also, the Elite Terminator Brother-Captain has the same statline as the HQ Brother-Captain, and costs the same, so you aren't losing out stats-wise. You can deep-strike these guys as well.
3) Fast Attack: Grey Knights. These guys can also deep-strike, or just set up with the rest of your FA choices. They can cruise across the board laying down a withering hail of stormbolter shells. If you have a shootier list, these guys could make a good counter-charge unit, perhaps. If your list is more assaulty-oriented, these guys may have trouble keeping up, so deep-striking would be a better option, most likely. Look into snagging a Teleport Homer if you want to do this, to bring them down safer. You'll want to keep these squads large: 7 + the Justicar is generally as small as you'll want to go. Also, vanilla is generally best. Buying special weapons makes these already awesome models even more expensive, and you sacrifice everything that made them special in the first place (increased strength, true grit, storm bolter).
4) Troops: Grey Knights. Same as above, but you can get two squads of them, in addition to the Fast Attack choice. They can't deep-strike, but everything else applies from above.
You can take any or all of the above, actually, depending on how much you want to invest in them. The Terminators are absolute terrors in assault, which is undoubtedly where you'll want them. The Grey Knights are more all-'rounders. They can do a respectable job laying down the stormbolter pain on the move, and dancing outside of 12" rapid-fire range. At this point you'll be out-shooting most other troops. They can also do a lot of damage in assault, as well. Also, be sure to read up on the special rules, specifically The Shrouding, which is like a slightly-worse version of the night fighting rules.
Hope that helps you make more of an informed choice!
Political language is designed to make lies sound truthful and murder respectable, and to give an appearance of solidity to pure wind.
If you're intruiged by doctors who are also ninjas, then this is the webcomic for you!
I play sometimes SM with allied DH. I use the SM as static fire bases (lascannon or missle launcher) and use PAGK for mobile fire support and counter-charge units. Sometimes I use them to go agressive, but that depends on your opponent.
You can use DH Terminators instead of normal SM Terminators, because DH are in my opinion much better than those of the SM.
A GM is maybe overkill, but if you use this one, you might want to get yourself a cheap SM HQ, maybe a Hero with Ld 10, so your whole army can use it. But this is only really handy if your have a lot of infantry. With a lot of tanks, dreads or other vehicles, you might want to go for the cheapest SM Hero you can get A GM is the real killer
Tyranids Win / Draw /Lost 
Daemon Hunters Win / Draw / Lost