Since we can vote for more than one, I voted for Martel, as well as Bido, because I kind of like him. This is not in the first anime, but the scene where Bido gets (FMA manga spoiler ahead!!)
killed by Greeling.. that was sad.

And, for FMA manga only chimeras, like others I voted for Heinkel.
On the side note, Heinkel gets kind of "choice" role among FMA chimeras IMO, being a Lion chimera, and given a bit of heroic role, and a likable character.
Coincidentally,
Heinkel is the name of a war plane, just like
Mustang and
Hayate. (As you know, Arakawa-sensei is known to be fond of using a name of plane, often war-time plane, as the name of FMA character.)
--------
<OT, Program Note, and other stuff:>
@JoshP1389 - Gahaha, yeah. ^^ And, we've seen quite a few "oldie" members coming back since the FMA:B started. Glad to see you again. ^^
On more on-topic note, for FMA anime (first series,) we have one more Chimera made by the same one who made Alexander chimera, and there is also a chimera that was created by Cornello and attacks Ed in episode 1, though these are not included in the Poll. (BTW, feel free to edit the wording and such, and also if you'd like to edit/change the poll in other ways, let us know and I or other Mod can change it. ^^)
@kkg22104 - Yeah, to be more precise, that was added by someone who made the fan-version of the translation for that scanlation.