Like you, Jalace, my greatest thrill is having a nurse make me drop trousers, pull down pants and bend over for injections. Unlike you, however, I rarely see my shots in advance because they are normally prepared after I bend over, which gives me more time to wallow in bare-bottomed anticipation.
"This might hurt a bit" is, of course, understatment but most excitingly frightening is being asked if I want to be held down. That means it will really hurt like hell! What particularly turns me on is asking if it will hurt and being told, "You might not be able to sit down for a day or so".