Honestly this won't be as long as Spcae Marines don't have many choices in either squad...and even less good ones. Still you need troops and there are some decent options so here we go.
TroopsHere we have Tactical Marines and Scouts. These are both very symbolic units in 40k in general and there are few people in the hobby that don't have a Tactical Marine lying around somewhere in their collection. Both of these recieved major changes for better and worse with the coming of the not-so-new codex, but since you need at least two from these guys, you have to know what to do with them.
Well here are the Tactical Marines...aparently the cream of the crop elite of the elite unit since for some odd reason a Marine starts in special forces and serves in an assault squad or dev squad for a while before they earn the right to become a rank-and-file bullet-catcher to keep the special weapon alive a bit longer. They cought what I like to call "body bag syndrome" from the older books meaning you really can't do much unless you take a full 10 man squad...again I don't know why. The nice thing is at 10 men, you get some free weapon choices and your veteran Sargeant is now stock instead of having to throw a few more points at him. You also have grenades stock, but Tactical Marines really don't belong in CC so big whoop. You also get the ability to combat squad with a 10 man squad, turning them into two 5 man squads. This doubles your scoring units, but frankly it's not all that hard to kill 5 marines. Of course it gives you the option of parking the heavy weapon and moving with the other half of the squad, but again 5 Marines aren't that tough to kill. My only big complaint, and it's a big one, is that they did get pistols but those pesky chainswords were just too heavy so they left them in the Heresy where their Chaos equivalent happily picked them up. They are a bit too expensive to just have one attack. I see the point of making them different then CSM, but having the greatest fighters in the Imperium with just one attack seems wrong. These are the Space Marine's signature unit, but I just don't like them and I think there is more bang for your point.
This brings us to Scouts. These guys did get a bit of a nerf, reducing their BS and WS by one. This sucks for Scout snipers since now Ratlings are the best mass sniper unit in the Imperium, but Scouts have their uses. I honestly think Scouts give you more bang for the point. Yes, you lose power armor and they don't shoot as well, but they're still T4 and S4 which is more then lots of troops can say. You can run more of them and you can give them pistols and combat knives for the two attacks. They can't take a dedicated transport but they can Infiltrate and outflank so that helps. There's always the option of the Land Speeder Storm, too, which we'll address in a moment.
I think probably a good way to go would be one Tac squad, kitted as you like with a transport, be it Rhion, Razorback or Pod you need some mobility. Unless you're running a character that takes advantage of equipment only available to tac squads (like Vulkan) I'd consider Scouts for the rest of your troops.
Since we're going from troops, I'll start with the Land Speeder Storm. If you're running scouts, this is a decent choice as a delivery system for them. It's less durable then a Rhino but it makes up for it with speed and flexibility. It also only holds 5 so you won't be winning an assault with just the squad inside, but as a combo the scouts make a decent choice. The Speeder contributs to combat resolution that round so that can help you hurt a squad. It's piloted by scouts so it's only BS 3 but its a good choice in a scout heavy army.
Beyond these are the Speeder squadrons. These can be a very potent source of serious firepower. First you can take them in squadrons of three which is fun. 9 Speeder lists will frighten armies that rely on CC anti-tank. Lets talk dakka. You start with a Heavy Bolter, which you can add a second to. This isn't a bad choice, but you can also mix and match between these, Heavy Flamers and Multi Meltas. A squadron of dual MM Speeders will scare mech armies or MC heavy armies. Mixing MM and HF will give you the flexibility to cook horde or melt armor depending on who you face. But wait, there's more! You can add Typhoon Missile launchers, too. These shoot 2 Krak or Frag missiles. Even better, remember frags are defensive weapons so it's completly legal to move 12" then fire a Heavy Flamer and two frags into a mass of Orks or Tyranids and see how lucky they'll be to roll 6's to hit you next turn. Yes they are armor 10 which does mean bolters will hurt them, but if played well these make a great option, and they're cheap enough points-wise to bring a few.
Along similar lines are attack bikes. These are often compared to Speeders and after really looking at both sides and the individual strengths and weaknesses to both I have to say its largely a matter of preference. Here you get stock Heavy Bolters again with the choice of upgrading to a Multi Melta. You can always fire your weapons and even have the option of assaulting afterward unlike the speeders, but you also run the risk of being tied up in CC. You also have to consider leadership as I personally have splattered one attack bike with a Defiler's cannon and watched the remaining bike fail its check and ride right off the table. They are cheaper though. Personally i think Speeders are a better choice, but if you like the bike models, rules or lower point cost better, go for them. Both will give you mobile heavy firepower.
Now we're into the less then stellar choices...
First Bike Squads. These are honestly only good if you bring a Captain on a bike to make them troops and even then... You do get to combat squad them and can bring an attack bike, giving the squad a mobile heavy weapon as well as an assault weapon. If they're troops they're good, but here in fast attack I just don't like them. I'll throw scout bikers in here too, because they are pretty equally useless, with the added bonus of not becoming troops like their power armored cousins.
Next we have assault squads. Honestly it's not that I don't like them so much as they don't fit in an army all that often. Most things Space marines have cost lots of points and as a result you really need to get a return on your investment and these guys have a hard time delivering in my experience. Again if you could make them scoring you'd have something but you can't. They're mobile, but so are Tac squads in Rhinos and they have the added protection of being in a box for at least a turn or two. I'd probably rate them higher if they could bring Meltas and pop a tank to assault the chewey insides, but they cant so meh. If you do take them, take 10 so you'll have more survive long enough to make a difference.
Finally we get to Vanguard. These guys are awesome. They come with 2 attacks base and have access to everything from power weapons to the dreaded thunder hammer/storm shield combo. They are very potent when geared out. Oh yeah...they're fast attack choices that are expensive base and then you have to pay more to actually be fast. Yes, here are foot-slogging fast attack units that are WAY too many points to be effective. Save them for Apoc, if at all. There are so many better ways to spend hundreds of points.
So here we are...You get two troops that are both useful and a mixed bag of Fast Attack choices. Some are just great and others are just there to get the number of pages in the dex up so GW could call the book the biggest codex they'd written. Cheap Rhinos and some effective fast slots are one of the reasons why Mech is such a popular tactic in 5th and it really started here so take advanatage of it and you'll have something decent on the tabletop.