So I've been solving puzzles here with moderate success and finally decided to try myself at creating one.
Here you go:

5) 01101101 01001011 00110100 01101011 01100011
4) 122 99 55 80 115
3) Let me tell you why you're here. You're here because you know something. What you know you can't Explain, but you feel it. You've felt it your entire life, that there's something wrong with the world. You don't know what it is, but it's there, like a splinter in your mind, driving you mad. It is this feeling that has brought you to me. Do you know what I'm talking about?
2) ZTVWR0M=
1) 43 67 78 36 44

http://www.steamgifts.com/giveaway/X#XXx

Hint:
diagonal (noun) :
A straight line which joins two opposite corners of a four-sided flat shape, such as a square

Solution:

Each hint should give you five characters code. Hints #1,#2,#4 and #5 can be decoded using this little thing. 5 is binary, 4 is ASCII, 2 is base64 and 1 is hex. In #3 you're just supposed to spot the bold letters. So here's what you get:
mK4kc
zc7Ps
ybEef
e5VGC
Cgx6D

That's 5,4,3,2,1 so don't forget to put it the right order 1,2,3,4,5. You'll get:
Cgx6D
e5VGC
ybEef
zc7Ps
mK4kc

Now let's look at the quote in #3. It's from the movie The Matrix. Not only that but the answer to the last question in the quote is actually "The matrix". You got before yourself a 5x5 square made of symbols and numbers aka square matrix. That quote was a hint to reassure you that you're on the right way :)
And then you just look at the pattern I gave and see where you can fit it. Or you look at the hint I gave later. There are only two choices - it's either slash diagonal or backslash diagonal, but look at the pattern again. The second character is a number and the only number that's second is in the second row. So the code for the giveaway is C5EPc. The game was Thief: Deadly Shadows.