Back in 2013, my friends and I thought "Wouldn't it be funny to draft a cube with only bears in it?" And that was a joke that we went with and I took up the mantle to compile a playable 360 list and it turned out that this joke was more fun than we could've expected. The initial rules was all creatures are 2 mana 2/2s and spells have the mana value of 2. This is still a pretty valid way of building it (and a friend has taken up the mantle of a more pure bear cube), but I've lately been experimenting more with cards that are "spiritually" (or in some cases literally) bears.
This cube is an interesting puzzle. It really makes you think about the questions of "What is a mana curve in an environment of no real mana diversity?" "What does an aggro decks look like when all the creatures are effectively the same size?" Games are often grindy which is to be expected when all the creatures are at base the same size. Things that grow on their own are very strong such as Kavu Titan and Kargan Dragonlord.
Power Outliers
A+B Combos
Anafenza, Kin-Tree Spirit or Melira, Sylvok Outcast any creature with persist (Lesser Masticore) and a free sack outlet (Altar of Dementia).
Chain of Smog + Magecraft (Witherbloom Apprentice, Leonin Lightscribe or Dragonsguard Elite)
These are the main things that I break the 2 mana value and 2/2 rules for. I feel that most of them make the environment better to draft and really are bears at heart.
White
It's prototype cost makes it technically a bear. It's big, it's powerful, but green has enough 5/5s with their Kavus with kicker that it's seems fair white gets something.
Blue
Blue has been having trouble a bit lately, so I took a deeper look at other mana values.
It's a bear. It's a 2/2. It's pretty interesting to have a creature that can be used on odd mana turns.
Almost every time, this is being cast for it's ninjutsu ability making it effectively a bear.
This arena only card is pretty easy to implement in paper. The cost reduction on it makes be a bear in my book, even if it probably will be cast for 4 most of the time.
This is another one that is almost always cast with suspend for 2. It adds a lot of oomph that blue is really lacking.
Black
None currently, I briefly tried a some 1 Mana 2/2s like Diregraf Ghoul and Vampire Lacerator but they felt like they were straying too far from the spirit of "bear."
Red
A 2/2 for one but can be dashed for 2. This one is probably the biggest stretch of my cheat cards. Like Diregraf Ghoul, this is more likely to get cut, but it's 2 mana dash ability is making try it out a little bit longer.
There's no real way to cheat this out early; you're only ever suspending this making it effectively 2 mana.
Green
This 1 Mana 2/2 effectively costs you 2 mana with its echo cost, just split up over 2 turns.
It's a 3/3 but it's a literal bear. When your opponent doesn't have a black permanent it damages at the same rate as a regular bear (6 damage every 3 turns).
This is a new one I'm trying out. Again being an actual creature type bear I'm more willing to cheat the mana. I'm trying out green being the "X" spell color since it fits with the traditional ramp identity of green.
C'mon, you know why this is here. It's strong when you've got thresholds it makes bears, it's great for green ramp.
Gold
A clone that's much bigger than a bear, it's kinda a big cheat. This is just a card I think is fun and is a payoff for ramp. Doppelgang is kinda of a decent replacement, but I'm running both for now and see how they run.
Lands
This cube does feature quite a few manlands that aren't 2/2s. My main rule for these are "dies to 2 damage." All of these should die to what would kill a normal bear. There is one notable exception with Crawling Barrens. This one does have the ability to grow past the 2/2 statline with only a small window that you can get it for 2 damage. Maybe this is an argument to cut it, but it's been pretty fine.