Metroid Prime has great enemies, but I can't call them all because that would be too long.
Favorite enemy from Prime:
A bit tied between Sheegots and Beetles
Beetles are from the start in the game, they're one of the first Prime creatures you'll encounter, everytime they spawn and making their sound makes me really feel like "Aww yeah! I'm playing Metroid Prime!" and then I rapidly shoot them down, they're a good new enemy that you'll encounter.
Baby Sheegots got my love too, I like the way how they awake from their sleep and sheds of the snow, then attacking you with an icy breath or ranged attack.
The Adult Sheegoth was also a great mini-boss fight, I like it's design and immumity to most attacks, and they'll even stamp to shake you back to the ground when you're higher than him. it's annoying, but smart nonetheless, it's a great creature.
Favorite enemy from Prime 2 echoes:
Gotta go for the Ing itself, They're creepy, and it scared me when I encountered and fought the first one, knowing that it was still dominant in it's own dimension. and I was still with only a ppower beam. and that's what makes them really interesting, that they're supposed to freak me out, much worse than the shadow beasts in Twilight Princess (Like, I can't really be scared of it with the wolf link fight theme >.>, the Ing theme compared is epic!)
I havn't played corruption tho, but I really want to.
Favorite bosses:
Prime:
Meta Ridley, I was already looking for that fight when I started the game, that fight was really intense, seeing Ridley in his armored metal covering, fully equipped with High-tech weapons, making him really a frightening enemy. and it was really a hard one too, I loved the whole battle.
Echoes:
Dark Samus, any encounter with your dark self is scary, you'll question yourself if you can beat it, (sadly for game logic, any boss you encounter is supposed to be defeatable), But Dark Samus was a badass fight, all her encounters. I've even saved the second fight on a different file
Corruption:
Even I havn't played it by myself, my favorite is, without a doubt, Rundas, Rundas is just one of the bosses you don't even want to kill, but have to. even the music fits that moment. Rundas' attacks in hypermode were incredible too, swinging a gigantic icicle like a badass.
Man...I feel sorry that Samus had to kill him...
...
...Favorite terraria weapons? Oh yeah...
Just keeping it short for now:
1. Laser Machinegun, it feels like going Hypermode in Metroid style.
2. Terra Blade, favorite Sword
3. Solar Eruption, It's a sword and it's fire! double yes!
4. Tactical Shotgun, badass
5. Flamethrower/Elf melter, because I like to burn things
Man, I spend like half an hour, if not more, in this >_>