I've been trying to beef up my portfolio lately, and what that boils down to is studying and rendering things more often. (Though my default is always sketches without shading.)
I don't know what that beast thing is, I just made him on the fly. I referenced poses from Hellboy (though I didn't copy) to study action and dynamism. The two poses on the right are referenced from an old anatomy book from the 50's.
I should disclose that these are drawn from Posemaniacs.com. There's no way a real model could hold the top pose. The bottom guy's legs are way too beefy.
I was practicing capturing poses, so I shuffled through Flickr and found photos of people jumping and did quick gestures based on them. Once again, useful for creating more dynamic poses. I like the guy on the bottom a lot.
These were done while sitting and eating dinner at school. The guy with the dreads came to ask me what I was drawing O_O. I didn't want to tell him I was drawing him. There was also a girl wandering everywhere talking on her phone, so I drew her a lot.
On these next few, take notice that I draw the parts I like, and generally ignore the head, feet, and legs. Oh well!