Kissing

There is no risk of catching HIV from kissing, no matter how hard you may want to tongue wrestle. Although very small quantities of HIV have been detected in saliva, your saliva also has properties that disable HIV so it would be impossible to swallow enough saliva to become infected with HIV. And anyway, when people talk about the potential risk of catching HIV from saliva they say that you’d have to drink pints of it, which apart from being an unpleasant thought, is extremely hard to do (see how long it takes you to fill even a small glass if you don’t believe us).
You can pick up herpes and glandular fever from kissing though, so it’s probably best to avoid kissing anyone with visible cold sores around their mouth.