Top Tier
Dancing Blade
DTilt
Fair
High Tier
Dolphin Slash
UThrow
Jab
Pivot Grab
Uair
Bair
Mid Tier
FTilt
DThrow
Shield Breaker
UTilt
Nair
USmash
FThrow
Low Tier
Counter
DSmash
FSmash
Bottom Tier
Dair
Dash attack
BThrow
Constructed with the same criteria El laid out. Notes:
Top Tier: My reasoning for placing Fair below Dancing Blade and DTilt is strictly due to it's limitations as a move in comparison to the other two. It is a very good move statistically, but it is merely that. It's application isn't as broad as the other two. Dancing Blade with transcended priority, good speed to range ratio, exceptional damage dealing and the best punishment game in Brawl, is undoubtably the best of the three. It also serves to aid recovery, can go through a plethora of moves, wears on Shields, and unlike DTilt, it can be performed out of a Dash. It's simply amazing. DTilt isn't quite as good, as Dancing Blade, but it beats fair in application. Great IASA Frames, good range and speed (this beats Meta Knights 1st FTilt hit box by the way), can DTilt lock, and can combo in to other very good moves such as short hop tactics, Dolphin Slash or even Dancing Blade. I'm dead set on the order of these three.
High Tier: Dolphin Slash is almost good enough to make it into Top, but not quite. It's major cool down time and lag hampers this move extremely (but for very good reasons). This move also has lag upon returning to the stage, even if you have clung to the ledge once using it before getting on stage. That being said, it's uses are undeniable. UThrow will likely surprise some of you, but it is by far his best throw. Very few characters in this game can beat Marths vertical game when he is below them, and even less characters actually have safe answers around this. UThrow sets up for all of them, and is the only throw (excluding DThrow and FThrow at 0 - 7% on the majority of the cast) that has a near guarantee follow up if you pay attention. It is also the only throw that keeps you safe after execution. Unlike the other throws, it also KOs. Jab is very fast, has IASA Frames, and stops almost all short hop games, which makes it a very useful utility move. Yes, I added Pivot Grab to the list, I don't care if you guys think it doesn't count. Marths Pivot Grab is like Snake's UTilt in grab form, and all of you need to start using it if you haven't. It leads in to UThrow set ups, and is a very good spacing tool. It's also likely his safest method to grab, barring your opponent isn't dumb and attacks your shield without spacing. Uair and Bair are very close, one will be used more than the other depending on your style of play. I personally use Uair more, since it's nearly unstoppable when the opponent is above you, and is your best option from a UThrow. Bair is a very good move as well, with longer range than Fair and good KO potential. Bair has bad landing lag however, so that brings it down a bit.
Mid Tier: As El stated again, FTilt suffers from being unsafe. That being said, it is very similar to Jab (you simply trade speed and IASA Frames for range and power), and stops a lot of svehort hop approaches. The few ones that Jab can't stop, FTilt certainly will. DThrow is the second best throw, merely because it gives you the most distance and deals the most amount of damage. It also substitutes for BThrow. Shield Breaker is one of the few moves that is very unsafe on block for the opponent(exluding PS) due to it's ability to wear down Shields. It has extremely long range, and is deceptively fast for said range. It also serves for recovery purposes, although can leave you vulnerable whilst doing so. UTilt serves as a good KO move (better than USmash I believe), is very useful against rolling opponents, but suffers from cool down. Nair is overused for many Marth players, as it can be SDI'd out of and has much less range that Fair. Fair also covers a larger area and has faster start up. It's KO power is substantial if you can land it, which is rare. This move is most useful in specific match ups where Fair is less desirable. USmash is good for sneaking in under opponents, particularly on platforms above. It's also the answer for a vertical KO where you can't walk the distance to use UTilt and Uair just won't cut it. It can be rather unsafe if whiffed however. FThrow over all is percent dependant. At very low percents, it serves as a good damage dealer and can chain into FSmash or Dair. At much higher percents, it's a good way to reset spacing. It becomes limited in the mid range however, because the opponent isn't sent far enough away to be safe and they can retaliate immediately.
Low Tier: Counter is very match up specific, and very situation based, but it can safe your *** when no other alternative is available. It is also the achilles heal to characters like Ike with his recover. DSmash and FSmash are sort of in the same boat, I only put DSmash above FSmash for the simple reason that it is faster on start up and it telegraphs less.
Bottom Tier: Dair does have uses, just seldom ones. Did you know that at higher percents where Fair won't kill Meta Knight from a Release Grab (either due to lack of damage requirement or being to far from the side), Dair is a better option? It will pop him up and you're automatically in an advantageous position, plus it does more damage. It can also kill most characters from a FThrow if they're careless and are grabbed at low percent. Spiking characters off stage also becomes rather easy with practice, especially foot stooling. However, it is very unsafe anywhere but off stage most of the time, and even there, you need to land the Dair, otherwise Marth dies. Dash Attack has decent power when tippered, and good speed. It has too much start up and cool down however, and it's only real advantage is either ledge guarding (which isn't half bad) or surprise tactics. It can also be used out of a few Grab Releases, such as with Pikachu.
Garbage Tier: Back Throw. Nuff' said.