Battlefield is obviously awsome, don't need to explain that.
Lylat/Smashville are great as well, depending on the character obviously.
Learing Rainbow Cruise and Halbred are essential to play Marth as well.
In Florida: Onett, Corneria, Hannenbow, Warioware, Norfair. Have always been banned in tournaments.
And here's why.
Brinstar is great, against everyone except Meta, because you'll die from UPB at early percents.
All of Marth's attacks have a tip, whenever you hit any part of the stage. For example the eggs or w/e those things in the middle are. If you Fsmash, then your attack lags, and anyone is hits is automatically tipped. Same thing with the platform supports on the sides as well.
Now if you Dsmash the middle, this will continually lag for a long time, (the whole time it's lagging it can hit your opponent FYI) if your opponent gets close he will get tipped and hit.
It is possible to Dtilt lock here as well, if you break like the top 2-3 of the eggs you can hit someone against the left wall with the Dtilt infinite.
Also this stage sometimes messes up rolls, so when your opponent tries to roll away, they'll get stuck in the middle.
Dolphin Slash will land you on the platform above as well so less lag time from Marth's fastest killing move.
With constantly tipping moves, and VERY early kills to the side, Brinstar is great against almost every character. For vertical kills, try Uair after the acid hits your opponent upwards.
Someone trying to camp you should not work either, will little escape room and Fairs chasing them this stage is great for Marth.
There's all you need to know about brinstar, I skipped the acid parts because everybody knows how that works.
And for those of you who don't Use Ganon and Arial SideB someone into the acid, you'll like what you see.
Also try to footstool someone coming out of the acid, it's just fun.
For anyone who doesn't believe this stage is great, here's me vs the best in Florida about a month ago.
http://www.youtube.com/watch?v=1twIJEqLbjk
Yes this was tournament, and yes I was very horrible for not grabbing the sypher, now just take a look at the stage use and tell me what you think.