obj2asm

[Trass3r]

> obj2asm tells the tale. (obj2asm is an incredibly useful tool, I don't 
> know why nobody uses it.)
> 

Maybe because it's not free (and not much advertised).
obconv also supports disassembling various object file formats + conversion between them and it's open source: http://www.agner.org/optimize/#objconv

obj2asm might provide something fancy that objconv doesn't but its page doesn't show anything that would justify paying 10$.