Weekends are some of the only times that many people have to sleep in. If you need someone to wake up, especially deep-sleepers, it can be very hard and frustrating to wake them up. In order to wake someone up, without wasting too much of your time, energy and/or patience, you need different techniques. The techniques vary in your relationship with the sleeping person. Whether you do or do not know them very well it is suggested that you don't do anything that you will regret later.
The most common technique is pouring water on a sleeping person. This technique works in waking them up, but that doesn't necessarily mean they will be happy with you. Another technique is opening the curtains in the room they're sleeping and pulling off their covers (if they have any on). This technique is usually more appreciated by the sleeper. Putting really loud music on is also very easy and effective. Metal music, out of tune music, or music they dislike, usually do the trick.
Some really fun ways that people have actually been woken up by are: smelling a fake cinnamon roll scent, that was sprayed liberally throughout their house/apartment, and waking up to someone saying, "Breakfast is ready."; having their boss call two hours before they are supposed to be at work and ask, "Where the heck are you?"; having a priest come to say a vigil over them and then have the master mind, behind waking them up, act incredibly surprised when they awaken; and having an air-horn blown in the same room as them. Note: if you use the air-horn technique don't blow the air-horn next to the sleeping target's head; you don't want them to become deaf.
A few other ways to wake someone up, that are a little less offensive, are: telling them something exciting, that will be happening later that day, that they are looking forward to; applying a gentle and steady pressure over the tragus of their ear, which is well known to make the sleeping person wake up with a smile; and, if he/she is a coffee person, wave temptingly, delicious smelling coffee under their nose.
As you can see there are tons of funny and clever techniques to waking people up over the weekend. Make sure you choose the right ones and know the sleeping person before you do anything too embarrassing.