I think a straight, married coworker of mine may have a mancrush on me. It's kind of cute. And fun. Because we can kind of sort of say flirty things occasionally without it meaning a darn thing. It makes our female coworkers raise an eyebrow, but I then remind them, "Hey, you make 'sexy' faces at each other, so don't go judging."
Now, a "mancrush" is not like a regular crush. Straight men can have mancrushes, as can gay ones. It's not necessarily sexual or romantic at all. It's like a "friend crush", as one female friend once put it. I've known a few straight friends who have had mancrushes. You can identify them by the almost giddy demeanor when they're around this (usually new) acquaintance and even the occasional remark or glance that could possibly be described as flirty, but not in the usual sexual way, or at least not in a way they'd actually ever consider following through on. Mancrushes don't always include flirtation, though. They may just seem extra happy to see you every time you show up, want to exchange numbers, talk to you a lot more than they talk to other male coworkers, etc.
But I actually enjoy straight guy mancrushes with the mild flirtation element 'cause you can sort of flirt in a completely benign way without worrying whether they will want to follow through with anything 'cause hey, they're straight, and you're not interested 'cause hey, they're straight.