Would be great to have one of our resident UA folks chime in, but based on what I've been told no cash (gift cards are a possibly gray area) and maximum of $20-something value (I can never remember if it's $20 or $25...but either way it's above my personal threhold for what I'd feel comfortable giving as a general thanks)

I've probably handed out a few hundred... wound up on Twitter a handful of times in pictures with UA employees, many very sincere thanks face to face, a few over-the-PA thanks, a couple stunned disbelief that I thought could turn into tears... and exactly one person -- an IAD GA -- politely decline. Touchingly a couple years ago I got a FB message from the widow of a recently-passed ramper -- Apparently he had kept my 'thank you' card from years before in his locker to remind him on those tough days.

My most recent endeavor I had a local bakery craft some travel-themed cookies (in individually sealed/labeled packages to try to mitigate the 'no food from strangers' risk). I've had more people ask where I got them from/how they could get more than anything else I'm still hearing about how good they were months later. (I made the mistake of giving them all away ... kind of forgot to try one myself )

Based on my experiences I can say fairly comfortably that the majority of crews (don't forget the pilots ), gate agents, rampers, etc. definitely appreciate a gesture of thanks from time to time.