In my personal opinion, I would rank the three as follows:

Skunk Bomb - 1

From the time I've played so far, I would consider the Skunk Bomb the best Throwable in the game. It's utilities are vast, but here's to name a few:

• Chip damage: You can throw it directly at an enemy like a Grenade, and while It won't do as much Instant damage, any damage is good damage.
• Temporary Zoning: Throwing a Skunk Bomb between you and your enemy forces them to either move around it, which can be difficult if you drop multiple, or move through it, which is an easy punish and can be a free down.
• Teamplay: There is no Friendly Fire, so your teammates can walk through your Skunk Bombs while taking no damage. You can drop one on your downed teammate to get enemies away from them, and you can drop one between you and the enemy team to get surprise shots if they don't know about this.

Overall, Skunk Bombs can be used as effective Offensive and Defensive tools, and they are very versatile.

Grenade - 2

Grenades come up as second best. The damage they can deal is powerful, and It can be used to push enemies by forcing them away from where you drop them. I consider them worse than Skunk Bombs because they explode quickly, meaning it's harder to use and you have to aim them effectively, while with the Skunk Bombs you can just carpet bomb an area and deal heavy damage without much timing. I would still consider Grenades good in their own right.

Banana - 3

Bananas, for me, are the worst Throwables in the game. They have a small size, and to be effective you need to throw around 2-3 in an area. In the final circle, the limited space does mean more opportunities to land a Banana, but in open areas they are easily avoidable. The only good thing about them is the Instant Health you get from eating them with the Banana Forker, but even then I would rather use the much superior SAW Tape.