On company's dime: $5 for pretty much any service. Works best with valet parking in my experience -- on day 2, my car appears within 2 minutes of my call, despite several people waiting on theirs. The 10 minutes saved that way are well worth the $5 for the bottom line.

Out of my own pocket: $2-5 on the last day (if MAGC; otherwise $2-5 a day), depending on how nice the place is and how dirty I'm leaving it. At the highest end -- if I have a suite upgrade at a StR, for example -- I don't shy away from $10 either.

Never thought about tipping for a service not provided. That seems silly. I also despise anybody tipping Uber drivers.