Ok.. I'll try to sum up the olimar match up.
I just made a thread about this because I'm afraid if I don't, then it will be lost in these 155 pages forever. And this took a decent amount of time to write.
First, I would watch these two videos, and watch how he gets the kills.
http://www.youtube.com/watch?v=haFiXIZilBA&feature=related http://www.youtube.com/watch?v=QmB0xBcBO8c
Gimping olimar is EXTREMELY important. It's what makes the match up in MKs favor. The goal of gimping olimar is to wait for him to use his double jump, then SL him. Don't worry about making your Dsmash go stale in this match up. It puts him in the air and near the edge right where you want him. Your Dsmash can be by olimars shield grab. So try to land behind him, or at a distance away from so that your Dsmash barely hits his shield. Being directly on top of his is a good place to Dsmash too. Basically, pretend his shield grab is the same distance as MKs. If you are in that range, don't Dsmash. If you land in that grab range, then you need to ftilt or dtilt as soon as possible. If you hit his shield with the ftilt, he will grab you after you complete all 3 ftilts. So instead I like to use the first 2 ftilt swings, then SL. That will usually prevent you from being grabbed.
Olimar hates grabbing the ledge, and you hate him grabbing the ledge too. So give him some space, and make it look like the stage is wide open for him to land on. This will set you up for the gimp. As he is approaching the stage, get under him (not directly under him, but close enough so that if he went straight down to the stage, he would be in Dsmash range). This will scare him and he will probably double jump. As soon as he does, you SL gimp him. If he starts dodging your SL, then next time just wait for the air dodge to end and punish (with a changed Dsmash/Fsmash/Nair/Fair are all good options). The trick is to be patient with olimar is in the air.
If olimar acts like he is going for the ledge, it's probably a trick. He will use his double jump and try to land on the stage. Be ready for it and tag him with a Dair like at 1:57 of the first video I linked you too. If for some reason he goes below the stage and tries to grab the edge with his UpB, then grab the ledge before he does it. If he simpliy falls on the ledge without his UpB, let him do it. Olimar only has too options off the ledge, and both of them are bad. 90% of the time he will use his get up attack very quickly after he grabs the ledge. So decently close to the ledge and get your shield up quickly. After the attack hits you, Dsmash! His other option is you jump. If you see the jump and you have time to punish it, then hit him with an aerial, and repeat the edge guarding process. If you don't have time to hit him with an aerial.. so what, olimar is in the air again. So wait for the double jump and gimp. Another safe option when olimar grabs the ledge is to tornado. I would just tornado if you need want more damage. Even if olimar drops below the stage when you tornado, he doesn't have many options. Move the tornado far enough away so that his off the ledge attack can't hit you (it has crazy range). When your tornado stops, he will either get up from the ledge, or he will jump. If he gets up from the ledge, it's safe to approach him with a grounded tornado.
Tornado! is probably the best move you have in this match up. Olimar has a VERY small shield, and your tornado can usually poke though it. The tornado will throw olimar in the air and give you a chance to kill or rack up more damage. Again, be patient while olimar is in the air. You don't want to do much of anything besides walking and staying under him (but not directly under) until he is about to touch the ground. When he is about to touch the ground, a couple things may happen. Either he will throw out a fair, or he will dodge into the ground. Sometime he may try to land directly on top of you with a Nair. Using tornado again will beat all of his options. The only thing he can do about it (and he will try) is save his double jump until you start your tornado. If that happens, you can: spam B as fast as you can and try to hit him in the air, or you can not press B at all and hope your nado ends before he hits the ground. If he is really high in the air, I would try to end the tornado quickly.
Another option when olmar is about to dodge into the ground is a dash attack. This is really good option if it looks like you're barely going to make it to him. If olimar is at low percents, Utilt usually combos very well after the dash attack and puts him in the air. Dash attack is also excellent for a quick surprise approach. If you're stand just outside of olimars grab range, then approaching quickly with a dash attack will usually connect. Don't just run across the screen and dash attack though! And need to do it when your already standing close to him.
When olimar is about to land, make sure you get the tornado out BEFORE he lands. If he can fast fall>dodge into the ground before your tornado gets there, then you risk him shielding it or pivot grabbing you.
you have more options than the tornado. Hitting olimar with an aerial, grabbing him, or even smashing him when he hits the ground is more devastating than the tornado. So if you are confident that you can hit with something better, go for it. The tornado is the safest option though.
Comboing olimar at zero percent is a little trickier. At high percents, he goes very high in the air and you can use the gimping technique, or punish him as he hits the ground. At low percents he doesn't go very high and comboing is harder. Like if you hit him with the tornado at low percents, it will pop him up barely above your head. Olimar will be coming towards the ground way quicker than you can get the tornado out to put him back in the air. Olimar will also be coming at you with a Nair, Bair, or Fair, depending on where he is at in relation to you. I wouldn't recommend trying to hit him with an aerial. It's difficult to aerial him when he is doing a Nair near your head! And if he can hit you with the Nair, it will lead into some crazy combo and you'll take 30+ damage! So when you barely pop olimar in the air, I would recommend just holding your shield. That way you can shield his Nair and punish it. The Nair has very little landing lag, and olimar will usually smash (sometimes grab) after the Nair, so be ready to punish the Nair quickly. If you're sure you can shield grab then do it. My favorite way to punish is to UpB out of shield. Even if he lands behind you where you can't shield grab him, you can still reverse SL.
If you decide to approach olimar with the tornado, make sure you short hop>tornado, don't start it on the ground. You want to hit him in the head with the bottom on the tornado. If you start it on the ground then you risk being pivot grabbed. It's fine to start it on the ground if you know he can't pivot grab (like when he is falling or when he is near the ledge). If olimar didn't have a full shield when you started the tornado, then it will poke through his shield. It's usually a good idea to start the tornado somewhat close to him. That way it will rip through his shield for an even longer time. The only time you want chase olimar across the stage with it is when his shield is low.
The most effective way to fight olimar and make sure your tornadoes connect is to Dair camp. You want to Dair camp him in a northeast or northwest direction from olimar. The goal isn't to actually hit him with the Dairs. Your goal is to make him shield or move away from the center of the stage. It is probably a good idea to try to hit him with one every now and then, but I would do this VERY rarely. While you are Dair camping, olimar will try to him you with Usmashes, Uairs, or UpBs. If you keep your spacing right, he should be able to hit you with any of these. Your Dair will also knock the pikaman away when he tries to Usmash, but the timing is near impossibe to do on purpose. If you throw out enough Dairs, you'll usually hit them away by accident. Good spacing off the ground will also make it easier to Dair olimar's Usmash attempts. Your spacing need to be low enough that you don't get hit with UpB, close enough that you keep pressure on him, but high and far enough away so that he can't easily Upsmash you.
When your Dair camping and olimar shields, that's your cue, TORNADO!! His shield will be wore down enough that your nado will eat through it. However, if it looks like his shield is still going to hold, then just retreat. Olimar isn't fast enough to punish you if you can get far enough away from him. And once you have retreated safely, his shield will be low from the last tornado, so short hop and chase him across the screen with it. The other option you have while camping is to dodge into the ground and Dsmash. Dtilt or Ftilt will work well too. Dsmash is higher risk and higher reward than your tilt options. I prefer Dsmash because in my experience, it usually connects.
When olimar is stuck in the tornado, you want to move the tornado so that olimar is stuck in the top left, or top right corner of the nado. If he is in the top middle, he can Nair you out of your nado and possibly combo you with an Usmash. I also think it's best not to do the rising tornado in this match up. Just press B about every half a second. That will keep your tornado out of the max time, and it will keep you from flying way in the air with it. You want to be on the ground as soon as possible after the nado so you can be ready to gimp/combo!
A popular edge guarding technique is to chase olimar off the stage and try to hit him with a Dair for Fair. I really believe that waiting patiently for him to come near the stage is the best option though. If you hit olimar very far away from the stage at a horizontal angle, then the Dair would probably be worth going for. But normally just wait.
There is a ton more I need to write, but I think I'm going to stop there
Commander Beef also plays ROB, so I can try to get some things up.
