I recently came up with an awesome idea for an Eggman mech. I call it the "Egg Reaper".
Basically, it's a 16' tall contraption shaped somewhat like a cross between a shrimp, a Nazgul, and the Grim Reaper
(most emphasis on the last one.) Its main coloration is a bright bloody red, but it also has a purple "cape" that it "wears" mostly for dramatic effect (and to enhance the Grim Reaper/Nazgul resemblance.) It hovers about half a foot off the ground (by default; it can raise or lower itself at will) using an antigravity device stationed on its bottom, kind of like what Diablon
from Shadow the Hedgehog
uses, only higher-tech.
Its most notable features are the two scythes
it has attached to its "forelimbs", which are its main weapons. The arms are attached to the robot at about "shoulder" height by default, but they can be moved down to the "waist" if necessary. Also, the cockpit is (as usual) the machine's weak point; it's located at the top of the mecha, where the head (or, rather, the face) would be, so it would probably be too difficult for Sonic (or another Homing Attack-reliant opponent) to reach unless the mecha is leaning down to execute an attack or he can somehow bounce off of the scythes. It can swing the scythes in a variety of fashions, all designed to overcompensate
for the scythe's ineffectuality in actual combat and to use the curvature of the scythe to enhance offensive power and/or inhibit attempts to dodge its attacks. It can slam the scythes downward, either independently or together, in an effort to impale an enemy; this is easy to dodge and tends to leave the scythes stuck in the ground, so it's a tactic that only gets used early in a fight. It can also bring the scythe(s) down to the ground and swing it vertically upward; while this has the same "easy to dodge" problem as the downward swing, it is less prone to leaving the Egg Reaper helpless and vulnerable to counterattacks afterwards. Its main attack, rather, is to swing the scythes repeatedly in a combination attack; unfortunately for it, the last attacks in the sequence frequently require it to lean over, leaving it open to attack. It can also launch the scythes like boomerangs at opponents who try to stay at long range (and I make the reference to boomerangs intentionally, as they return to the Egg Reaper after flying a set distance). Speaking of long-range attacks, it does have some missile launchers, but it uses those very infrequently, as it prefers to fight at close range (and even at long range, it prefers to use the boomerang attack.) When Eggman decides to stop toying with his opponent, he steps things up by having the Egg Reaper bring its scythes down to the ground and spin them in a circle while chasing the foe. Finally, when desperate, the scythes can emit fire, amplifying their attack power and making it downright impossible to touch them without getting hurt.
As for the Egg Reaper's battle theme, I'd have to go with "Execution Day
" by Meat Loaf. (The first version is the main battle theme, while the second is the "pinch" variant.)
Edit: Found the studio version of "Execution Day".
Edit (again): The first link may be defunct, but I saved the music from it, and I've uploaded it to my Dropbox account. So now you can listen to it there.