In Deus Ex: Human Revolution for the PC, PS3, and Xbox 360, there is an exploit in the hacking system you can use to get as much extra XP as you would like.
The trick is to find a security system with a datastore (the cube shaped node) that gives a decent amount of XP as its bonus, and that’s relatively easy and quick to hack. The AJensen computer in Sarif HQ is a fine example, since the datastore on that computer gives +500 XP on a successful hack.
First, save your game in front of the security system. Now, initiate the hack, and make sure to hack the datastore node. When you have successfully hacked the security system, but BEFORE you press the button to exit the hack, load your saved game without progressing past this screen. For some reason, the game will keep compounding the XP you get from that datastore, and when you finally progress past that screen, you will get the bonus XP multiplied by how many times you loaded and did the hack.
For example, if you hack AJensen’s computer and get the datastore ten times, you will end up with over 5,000 bonus XP.
Another tip is that you can use as many stop worms and nuke viruses as you want while you’re doing this to make it faster, since you’ll be reloading your game every time anyway.
This can and probably will be patched later on, so I would avoid updating the game if you want to keep using this exploit.
Check out my other article if you’re in need of some hacking tips, or a complete guide to hacking in Deus Ex: Human Revolution.