Combustable Lemons for Portal2, Garry’s Mod and Left 4 Dead 2.
Since people won’t shut up about it, I hacked together this little pack initially for L4D2, then stripped it back for GMod, Portal2, etc. It should work on most source games, but failing that, give me a shout, and I’ll do my best to update it.
All instructions are included in the .zip file [Download]
If you want to find out how it was done, have a wee look at this tutorial: