The standout one for me was my Team Leader at work. I crushed on him like crazy! He was funny, cheeky, in his early forties but married. It very much distracted me from my work. Workplace crushes are the worst.
In general I develop crushes on friends of friends. And they are usually guys that aren't conventionally attractive. I have crushed on chubby guys with messed up hair, nerdy looking guys with way more brains than me and really posh snooty guys too.
I'll flirt with them a little but my friends are usually disgusted and advise me not to go there. I lost a really sweet guy that I had a little crush on who eventually sent me flowers and asked me out, but as he was nerdy looking and part of a church group some of my friends didn't like him and I wasn't strong enough to disagree. oh well such is life ...