I gave this to Peter Cullen (G1/Movie Optimus Prime) at this year's BotCon. It is not submitted to my deviantArt account yet because I have fallen greatly behind on there (because you can't do ANYTHING on there on with a 28kbps or lower dial-up connection) and didn't want to add to the mess that needs serious cleaning up. I'm supposed to be getting a cable modem back this Saturday so I'll finally be able to clean up my dA stuff. Until then, kudos to Photobucket!

My reference was Ultra Magnus' "ghost Prime" in the Ultimate Guide to Transformers book I have. I just changed the colors to follow Optimus Prime. I matted and framed it for him with my signature in ink. He loved it! He's a really great guy and adores his fans.
Mediums:
Pencil, then inked
Photoshop (coloring)
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BW Megatron
I gave the original to David Kaye (BW/BM Megatron) at this year's BotCon as well, matted and framed. But like the one above, this is not submitted on deviantArt yet. He loved it and had my eyes watering with his comments, and then he laughed at the rubber ducky I stuck in there behind Megatron's foot (straight from the show). After all, he knows all the rubber ducky jokes and whatnot.

Medium:
Pencil
References:
Beast Wars Season 1 DVD; episode "Power Surge"
Beast Wars Season 2 DVD; episode "The Agenda Part III"
Beast Wars Season 3 DVD; episode "Feral Scream Part II"
Beast Wars Season 3 DVD; episode "Master Blaster"