The black outlines feel off when you have nice, far more subtle, coloured outlines on the other two pieces. Those blue spike things on the first sword... what are they? Ice? The outline is too intense.
Most importantly, none of these look sharp. Well, maybe that two-pronged one. The others look like they're made of rubber. If you want a more sharp and intense look, colour them more intensely. Except those ice things, they need to be calmed down.
I'll try an edit in a moment to further explain myself.[edit]
Alright so there's yours, mine, and mine without the ice spikes or whatever they are.
While colouring, I didn't even look at yours except for a brief glance for the light source, which may have been a mistake as far as the ice spikes, if only because I could just barely even grasp the shape they were supposed to be. On the middle ones, I actually matched the shading you did, so you had something going right there. The others I guess I kind of just shaded as blobs. So, ignore the shape the colours create. The way I coloured it is the important part. I guess sel-out is what I'm trying to sell you here. There's also the range of levels in the colours, and the colour choices themselves. Metal grey is not always grey, especially when surrounded by blues. My colouring is even rather tame and withheld considering the possibilities.
Hope this helps.
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He's the man who invented pixels. His name's Ivan Pixelle.