Was curious about everyone's likes/dislikes.
For me:
Favorite: Thresh. Constant opportunities for zoning and landing the perfect hook. Plenty of souls to harvest. Close second: Yasuo. Super-fun mechanics, no mana costs, plenty of windwall practice.
Least favorite: Trundle. Get harassed like crazy early, lack of a dramatic initiate, pillar is his only peel.
Favourite: AP Trist or AP Shaco Least Favourite: Ao Shin. He's so useless, it's almost as if he's not even in the game yet STARE
My favorite is Varus. Snipes for days and has pretty boss waveclear. Not to Mention it's far easier to hit a 5-man ultimate.
Least favorite is Tryndamere. He's astoundingly useless in ARAM.
I have to disagree with you on the Trundle, I've carried some ARAM games pretty hard with him.
Anyways, I tend to like champions that can make early plays (ie Pantheon, Amumu) if I get a melee champion. For ranged, I like more teamfight oriented kits (ie, Sona, Varus). I also like super mega tanks, specifically Malphite and Nasus due to their unfair mix of damage and tank stats.
I don't like single-target assassins (ie, LeBlanc, Talon) because it's really hard to pick off a single person without a Blitzcrank on your team. I also don't like late game scaling champions (except Nasus, for reasons stated above) since ARAMs don't always get to late game.
Clearly you have never played full AP nasus
Favorite: Trundle - Runs at you for days slowing everybody and those pillars that pin people are the best. Second: Volibear - See above except replace pillars with flipping poor souls
Least Favorite: Teemo/Shaco - Roit pls Second: Poke Champs - Boring
Honorable Mention: Lollipoppy - Secret S++ tier. Don't mess with her
Favorite is Leona. The amount of YOLO that can be had is hilarious, as well just being generally good for ARAM's constant fights.
Least favorite.....I have a few, but I'll probably say Evelynn, her passive rarely comes into play and if the opposing team is all fighters....well.....you're not gonna have a good time.
Syndra is my favorite because I just love the champion. She has damage and utility and scales throughout the game. She is probably my most played in ranked as well.
Least favorite is Tryndamere because he is literally useless until you get two items.
a tough question... I play aram to enjoy random other champs i rarely play... though ap ezreal is pretty awesome :P
least favorite... again tough... have to be tryndamere though, I never liked him, still dont, and probably never will. Udyr is a very close second
Favorite: ANIVIA. Grab a Catalyst at spawn and don't back until you have 20 assists because that's how long it will take the enemy team to kill you. Power level Crystallize first and laugh when people engage and then can't get back to the safety of their team and feed. (Ironically, I almost never play Anivia on the Rift, but in ARAM I get her fairly often)
Least Favorite: Twisted Fate. Destiny/Gate is really pretty useless and without a steady stream of minions it's hard to build up Stacked Deck correctly. Twisted Fate and other "opportunistic champions" who have to build up their kits to get their assassination off have a rough time in the chaos of ARAM.
Strong poke champs are my favorite and im sure the large majority of the player pool:
Ziggs Nidalee Vel' Koz
Do love me some Thresh and Nami in ARAM also though, great for making big plays.
EDIT: Least favorite would be melee top laners with a few exceptions (jax is still pretty fun).
I'd say one of my least favorite Champion to play in ARAM would be Nasus. Yes he can still be good if you max E over Q, but you still won't get the Q stacks you would get in a normal game. It kind of defeats the purpose of Nasus. Favorite? That's a real hard one. There is a lot of champions that I enjoy playing in the ARAM. Post rework Nid was really.... interesting in ARAM due to the small map size and how easy it was to hit the Q on the one lane.
Favorite: Fiora. I always seem to do well when playing fiora and always have lots a of kill participation and fun when playing her.
Least: Nocturne. I never do well with noc in aram because his kit does not work well for aram and just get poked out before i can ult in.
Leona by a pretty good stretch. It's not because I play her that well, even, it's just such stupid balls-to-the-wall fun. She's fun to try with different builds.
My favorite champ in ARAM is Ahri, but I just like playing her in any format.
I generally don't like getting melee champs when I'm facing an all ranged team. Whenever that happens, I tend to rack up deaths.
Favorite: 
RQWEQWEEWQEQWEQWEQWEQWEQWE
Least Favorite: 
everybody hates the croc and I get kited to hell and back :(
Honorable mentions: 
Least favorite: Cho'gath. He is the only champion (as far as I am aware) who has to lose power (stacks) in order to shop in ARAM. Losing half is brutal too, esp since it rounds down :( (Draven can time it so he dies with 0 stacks of adoration so he doesn't have to lose any power to shop)
When they did the Rengar trophy re-work they dropped the losing stacks, which I think was a good idea.
favourite: Lux i guess
least: Sion, in any map any day - can´t wait for the rework
Favourite: LULU! So much poke.
Least favourite: Master Yi because I always end up feeding.
Xerath, Vel'koz, Karthus, et cetera. Really, any AoE mage (which is to say, most of them) are really fun.
Just had a 
game in ARAM... holy crap Full AP Karma wrecks everything. 10/10 would recommend.
Least favourite? Probably 
. Building tanky is worthless and building AP nasus just feels cheap.
If the other team has poke, I'd rather have a poke/ranged champ, otherwise it's kind of miserable.
Favorite: usually Karma, no reasons needed. Runners up: Malzahar, Diana,Yasuo, Zyra, a few others I can't recall at the moment.
Sometimes I like Ziggs or Nidalee, but seeing them all the time gets really boring really fast.
Least favorite: Almost all melee fighters or assassins like Tryndamere or Evelynn. However, what I like even less is getting one of my favorite champions with a team that has no chance (whether for comp or afk). Nothing worse than playing a great game and still losing for factors you couldn't influence at all.
I love Nautilus in ARAM. Once he gets 3 items and boots he's an unkillable teamfighting machine.
He can also build AP and become the ultimate tank assassin.
"The unseen Nautilus is the deadliest." -Me 2014
Least favorite: Garen. I just... I have always disliked Garen strongly.
Favorites: Ziggs: Bombs everywhere! Karma: Qs and shields! Lux: DEMACIAAAA Varus: Q Snipes!
Least Favs: Rammus: not ok Nasus: Unskilled people go AP/CDR Skarner: pre 6 garbage Udyr: Cant do anything unless they're in melee range
Favorite-Dat Teemo, Nidalee, Ashe, Kayle
Least favorite-Urgot, Alistar, Garen, Jax
Favorite: MORGANA (my fav. champ anyway, gotta love dat bind); KARMA, Ziggs, Nami, Leona, Thresh, Syndra, Zyra.
Least Favorite: Kassadin, Melee-based champs.
Favorite: Maokai. A mobile castle, kills everything, doesn't give a damn and can't die. Overall tanks are fun on ARAM.
Worst: Udyr/Hecarim. Running around and barely doing anything.
Trundle can be real beast on ARAM, but you can't build him like you do on SR. Play him like a troll, get full CDR and max Pillar (E). With 40% CDR and 5 lvl E it has 6.6 cooldown and you can both peel for your and catch enemy people out of position to punish them. Every 6.6 second. Enemy cannot do a single mistake.
My favorite is Ezreal. You can go AP or AD and your ULT is just fun. Least favorite would have to be Skarner.. You get poked down before you can get anywhere early.
Am I the only one that likes Urgot in Aram? Urgot is actually good in Hallowing Abyss because of a better availability to Q and back when it was 1 for ten Urgot's Ult had insanity chains (Suppression after suppression)
Favorite - Skarner - excellent harass w/atk speed & spell blade. Most importantly, giving folks a ride on the Skarner express!
Least favorite - Taric - Why did I buy Taric!!!!!
I play a lot of Leona/Shyvana, so it's always nice when I get them as opposed to free week Urgot :P My favorite would probably be Lux, since she's good at poke and burst, has cc, and I can play her reasonably well. Karma, Janna, Soraka and Varus deserve honorable mentions. Least favorite, well, I hate short-range mages, so any time the dice say Annie, Ryze or Nunu, I want to reroll. Melee carries (hi, Yi!) are also something I don't like playing.
So, I guess I just like poke on anything and tankiness & burst on melees.
I like any champs that has a long range so that I can poke down the enemies down! Like Lux, Vel'koz, Jinx, etc. And I like tanks too! Rammus, Nasus, etc. I find it entertaining to see everyone on the enemy team targets me and slowly draining my HP bar and all my team came and make the plays! c:
My least fave are the champs that has physical attacks unless they are tanks. It's hard to poke them down and I find it harder to try to get kills because my teammates who are ranged and just take it away without being touched which struggles me the most
Favorite: I'm not quite sure who my favorites are but I enjoy playing practically any ADC since that's what I main in ranks
Least Favorite: Rene or Trynd. Any champion that relies on getting hits on either champs or creeps to have it decay I find a travesty on ARAM
Favorite: 
COW PRESIDENT OF RIOT, INC. Closely followed by my girl 
. I also have to throw 
in there due to a match where I went 7/1/23.
Least Favorite: and 
. It's hard to get tanky enough with Renekton early on, so you have to be at least decent to get started with him (I'm not decent at Renekton). Soraka is my least favorite champ though...she's like a poor man's 
. Sad face.
My favorite: Kog Maw, whether AP or AD, because he's either a poke monster or a tower shredder and his passive synergizes so well with the map. Close second: Caitlyn, because her poke and traps are phenomenal. Least Favorite: Udyr or Fizz, because they have to all in, 0 poke skills.
Love veigar, raka, and morg. super OP in aram. HATE POPPY. can't figure out how to play her or what to build
