I'm surprised no one has said Ziggs yet.

Massive AP burst damage combined with most of his spells being AoE make him prone to pentakill entire enemy teams over and over.

Hell, I got an easy quadra kill a couple nights ago with him just by slamming my fingers on qwer and clicking rapidly.

My only Penta was as Mordekaiser, but it was totally deserved. It was a 1v5 because my team was already dead, and the enemy champs were all at almost full HP. I killed vayne with my ult, and used her ghost + my guardian angel to kill everyone else. It was pretty epic.

We still lost.

Only got 1 with Rumble (though I almost got a second one time)... back before his ulti got nerfed a bit. It was that path to the central tower near the baron and red buff. Malphite pulled their entire team into my ulti and I just moved in to finish the job, everyone else had died in a bad team fight, but managed to weaken them some.

Champions with a good AoE attack probably are more likely to get a penta. But really everything has to work out almost perfectly and the enemy team has to set themselves up for it really bad lol.

I have scored two pentakills. My first was with Mordekaiser and it was a legitimate pentakill where I stole the ghost of the enemy teams best assassin and then I killed all 4 of his allies while my team wandered around the map for no reason. My team was totally stoned(they admitted to it not even making it up) so we lost anyway.

My second pentakill was more conventional we were teamfighting over by red buff and the enemy team focused down all 4 of my teammates except for me, but they were all pretty low health, and I was a fed caitlyn so I killed each one before they could take more than a couple steps towards me. The last one tried to run, but he didn't make it. We ended up winning the game since an already fed carry with an extra 1500 gold was kind of the end for them.

I have scored 3 or 4 quadrakills with Kayle over the course of my matches, but I can never quite seem to get the last guy or he is hiding around his nexus or something.

I have seen Riven, Cait and Trynd doing pentas.
Dont remember about others now

I'd say there are three types of champions that get pentas.

Type one is champions with mobility skills(especially if there is a steroid or some form of crowd control built into it OR the champions has a low CD CC option) that refresh cool-down upon getting a kill, this class includes Yi, Akali, Eve, Katarina, Irelia and Tristana off the top of my head, these are the guys with the best chances of penta, starting with champs like Akali, Yi, Eve, Katarina and Tristana... Irelia is actually pretty dang hard to get a penta with compared to the rest of this crew because actually has to kill with her mobility move itself for the cd to refresh, but on the upside if she can one shot minions with it she can always get around that way and use her OTHER capabilities on enemies... Eve actually is pretty strong for pentas because she gets health regeneration and a refreshed massive move speed and attack speed boost ultimate any time she gets a kill.

Type two is the champions with very difficult to pull off but incredibly powerful moves (Nunu, Katarina, possibly Fiddlesticks and Karthus) that if they manage to get all their timing right in the gap where no one has CC available can do a ****ton of damage all in one go on a lot of people. As you can see, Katarina actually belongs to groups one and two... however she can pretty much be completely shut down by one halfway hard CC at the wrong time, so she only really has a better chance of a penta than other members of either group versus unorganized teams or poor players.

Group three is ANY AD carry late game. These guys shovel out such an insane amount of damage that they have a pretty good chance of getting a penta out of a teamfight (but only mid-late game) sooner or later, the especially nasty ones are the ones like Vayne, Ashe, Sivir, Tristana and Kog'Maw who are really really hard to escape from after a losing fight. Tristana is in groups one AND three WITH A STRONG SLOW ON HER REFRESHING MOBILITY MOVE, endgame built she can also put out a ****ton of damage with excellent mobility and a bit of aoe damage any time anything dies. To top it off she has quite possibly the most powerful positioning skills of any ranged AD carry and the second longest auto-attack range of any AD carry ever, only losing to Kog'Maw when he's using Bio-Arcane Barrage once she gets to level 18 because of her passive.

The three top champions I would call for getting pentas are Tristana, Katarina, and Akali. However, smart cooperative decently built teams are pretty much guaranteed to keep Katarina from doing anything, and 125 gold once or twice can practically destroy Akali's laning phase if done early, so I would actually say that the strongest of these is Tristana, due to there not being any easy way to shut her down, she even has a built in healing reduction effect to make sure that Soraka/Sona/Alistar/Taric/Karma/Janna/Sion aren't saving her target easily.

My first penta was with Nasus, I was the only one left alive lol, on both teams

The only champ I've managed it with in real match, was Skarner, honestly not sure how it happened, I was doing well jungling like 8/0/3 then suddenly a team fight broke I get a double kill as 3 on our side die and then cleaned up the rest via Q/W/E spam for penta...

I have gotten three Pentakills; Nocturne, Jax, and Yi, in reverse order.

Champions with high burst damage and AoE are better at pentakills than champions with high DPS and gap-closers. Although both can get them, If you just burst them down in half a moment, you have more time to get a Pentakill than with DPS. So, I'd say champs like Karthus, etc.

Nocturne is a difficult one, but possible; use his ultimate to initiate, then use his Q on their entire team. Now they're all trailing speedboosts for you and a nice AD buff. Burst one down with high AS and your passive; use your W to keep their mage from killing you. Then, pick off their second person with his E, completely frying them. Chase after them after these first five seconds. If you built him right, you get a nice little Pentakill.

Jax...I just got lucky. I turned on my stun, leapt into a teamfight right near the end, and the AoE made them easy pickings.

Yi is obvious.

Champions with high burst damage are virtually all single target. The exception to the rule would be Brand. If the enemy team is smart enough to peace-out if the fight starts going south there's no way for brand to catch them outside of a lucky ult bounce. Akali has high burst... with a refreshing gap closer.

You just said that champs with burst are better, and then you said that meant Karthus would be good... Karthus is one of the definitions of a dps mage along with champions like Malzahar, Cassiopeia, and Ryze. He has no burst to speak of outside of his ultimate... just really high dps if used skillfully. Dps champions are better for pentas than burst champs because burst champions have to get lucky and kill pretty much everyone in the same burst... which virtually never happens, then the burst is on CD and you aren't going to complete that penta. Dps champions can keep on dishing because they have either low spammable cool-downs or powerful auto-attacks. They can keep on killing without having to wait 10-30 seconds for their burst to come back online.

You stated that burst champions have more time to get a penta... this is stupid, what you really mean is that IF THEY ARE GOING TO GET A PENTA it TAKES more time because they have to wait on cooldowns. Dps champions can finish that penta up in far less time, and therefore are more likely to get it before someone escapes. Gap closing champions are hard to escape from.