It's been a while since I've had a good think about this, so let me see...
10: Twin Twist
I'm not a huge fan of the Bruticus/Ruination combiner, but I have inordinate amounts of fun with this guy. Also, the drill weapon is pretty awesome.
9: Senator Ratbat
The Generations Scourge Mold is
all right, but seeing it in royal purple and gold? f***ing awesome
8: Cosmos
This little dude accurately captures what 3rd parties haven't been able to attain. He's awesome simple and fun. His partner is a decent guy as well.
7: Arcee
To quote Tychus from StarCraft 2: "Hell, it's about time." While I like the Takara version a little better, there's no denying that a splash of pink can make a collection pop.
6: RhinoxIn continuing on with Beast Wars, out comes this hulking beast. He is downright perfect in any way, and a great homage to his original character.
5: ScoopThis dude is so very under appreciated.
4: METROPLEXHe's big, he's monstrous, he's a freaking city! He would be higher up the list but he's pretty hollow, and surprisingly simple (thought that's not always a bad thing). You cannot beat him for presence though.
3: JetfireHe's hollow, but he's pretty awesome nonetheless! Personally, I got Takara's because I didn't like the chrome on this one.
2: Ultra Magnus (reserved)I don't have him yet, but I will, and he'd better be as awesome as I think he will be!
1: SpringerWhile there are quibbles that can be made about any of the previous 9 figures. There is absolutely nothing wrong at all with this toy. He is the current embodyment of perfection that HasTak should aim for every time.