One drops are the least important thing in any draft or sealed pool. You shouldn't play them pretty much ever. They typically do little for you, don't fit random cards, or just suck. And why should they, you aren't expected to win the game by turn 1(not counting you Legacy). In constructed, it's a whole different ball game. You have these cheap cards that actually interact with other cards in your deck. Not only that - your selection is a lot wider and if you look deep enough, you can find cards that can really put the pressure on.
The number 100 just kind of worked out. There are approximately 600 one costed creatures, and I honestly only checked out about 400 of them - top half and the very bottom(maybe I trust The Gatherer too much, but I'm always open to suggestions!). I found 95 that I really liked just naturally. The other 5 are included as my bottom 5, but 100 of course just sounded better.
I could have forced myself to get 5 more, but there are essentially 7 duplicates that you will see actually bringing the total to 102.
The 5 Worst:
5. Kitsune Diviner
I'm sure it's decent in a block draft, but in any other scenario it's a completely unplayable 0/1 do nothing creature. Ornithopter, Phyrexian Walker and Shield Sphere are all cheaper and better.
4. Wall of Wood
One of the original cards and it's hard to hate on my man Richard. How bad is it? Well there exists a 0/4 artifact wall, which makes this strictly worse than that. Artifacts are supposed to be toned down because they can be played in all decks. This thing though if made today would need to be a 0/5 at minimum making this permanently awful.
3. Crazed Goblin
1/1 for one was somehow too strong. No one was playing Mons Goblin Raiders before. This is the kind of card you would only add if trying to make one of the worst decks of all time. At least the Impetuous Sunchaser has haste and flying. The only good news is that it doesn't have a drawback that can ruin a game plan, unlike this next card.
2. Alabaster Leech
This actually made my number 6 for the worst creatures of all time. I mean, what kind of a drawback is this? It puts you a complete turn behind for a 1/3 on turn 1. If it were a 3/1, we might be having a completely different conversation.
1. Primordial Ooze
The only one drop that can straight up kill you single handily if you aren't prepared. It requires a serious amount of mana commitment after you play it and doesn't even have evasion. If you didn't have to tap it then maybe it's at least a clock. Even if you hit for two damage on turn two, you are permantley behind in mana, or you are going to be behind in life quickly.
The standard that I will set every creature on this list to. The very first thing I think of when I hear aggressive one drop. It's the first thing that used to make a White Weenie deck. It's just outclassed occasionally by better cards these days.
95. Orcish Spy
You are not going to be breaking any games open with this guy. But being able to look at the top three cards of your opponents libray is no slouch of an ability. Being able to plan ahead can be a pretty big advantage for one mana.
94. Pulse Tracker
It's clearly more dangerous as a multiplayer card, but it is swinging for two damage on turn two. A nice Vraska/Jace flavor text. Even when it gets outclassed you don't necessarily have to chump block with it, just add that extra life loss.
93. Nova Cleric
Sideboard only of course. There are many creatures that can blow up enchantments. None of them except this guy can take out all of them. Sure you could just play some sorcery that can probably do the same thing, but maybe this gets some damage and in the meantime forces your opponent to hold back in some scenarios. An extra point of toughness is worth mentioning as well.
92. Honorable Scout
Another sideboard card, this one also works better with more opponents. How much life would you like to gain to consider this playable? Eight life maybe? So that's four creatures, not hard to pull off though it's clearly not a pure one drop either. Eight life and a chump blocker would be borderline playable for one. Works in U/W control.
91. Soldier of Fortune
It's at the very least mildly annoying. At best, it's a sideboard card against all sort of tutors. It's a permanent answer to these cards that do top deck manipulation. A card I've always wanted to play that never quite had enough umph for me to play in one of my constructed decks.
90. Treefolk Harbinger
A Wall of Wood that will minimally fetch you a Forest. Could be good or bad, the ability potential at least makes the card relevant. Being able to grab another Treefolk in a Treefolk deck is what sets this apart and sets your deck up for other shenanigans.
89. Tormented Soul
Obviously if you can take advantage of the unblockable ability it gets better. Aggressive decks only would think about this. It puts that 20 turn clock on. Works well with Bloodthirst and Exalted. Equipment makes it dangerous as does other pump-like auras.
88. Goblin Gaveleer
Speaking of equipment, adding a mere +0/+3 Kiteshield(arguably the worst equipment) makes this bugger a 3/4 Trampler. Not too shabby. It's at minimum is a 1/1 Trampler with a useful creature type. Comparatively speaking, that's not bad. That art is pretty funny as well.
87. Ezuri's Archers
I've always wanted to like the Archers more. I just don't as much as I think I should. It's definitley a sideboard card. A 4/2 reach that can stop small fliers is a sweet deal for a mana. In other scenarios you are stuck with your vanilla creature.
86. Guul Draz Vampire
I like that late game it becomes relevant as well for a one drop. That is a major thing I want in a cheap card, to be useful in a late game scenario. If you are aggressive and your opponent isn't Black, it can be a real problem.
85. Hada Freeblade
You wouldn't play it if it weren't in a Ally deck, that knocks it down a few notches. But when you do play it, it's a great staple of said deck. It can grow quite big, even making it a better ability than evolve.
I don't like that you have to tap it. If you could attack and still only use it's ability once a turn it would be much better. But as it is you get a larger blocker every turn. It just never does what you want. If your opponent has a larger creature, it won't be blocking alone and surviving. If your opponent is reeling, there is not a good answer to if you should just attack with a smaller creature or hold off.
Thallid is much better served being played during turn one opposed to late game. It also works much better with a concentrated fungus deck. It may not be playable outside of that theme deck. As for Utopia Mycon - getting mana for your Saprolings is a slightly better deal. You still don't play either of these unless you can do something with all the cranked out beasties (ex: Thelon of Havenwood).
82. Martyr of Ashes
Probably an instant Pyroclasm at minimum sitting in play. You do need to keep two mana open and doesn't affect pesky fliers, but it can also potentially deal 4-5 damage for a mere three mana. The real problem is it doesn't really work with other strategies, or at least any I can think of. If you think you are running into weenies, just play Anger of the Gods or some equivalent. Red has too many answers to truly look here.
81. Diregraf Ghoul
I don't think the comes into play tapped drawback is that big of a deal. So it can't chump block immediately if played late game. So what. Can't block creatures on the draw? Also not the worst deal. If you are going aggressive it's clearly solid. Would you rather play Felhide Brawler, Fleshmad Steed or heck even Tormented Hero? Didn't think so.
Check out my other posts:
The Top 10 Planeswalkers
The Top 20 Land Cards
The Top 20 Theros Cards
The Top 20 Dragon's Maze Cards
The Top 20 Common Cards
The 30 Coolest Dragons
The Top 40 Black Cards
The 80 Worst Creatures
100 Unique Creatures
The 100 Worst Cards