Are some real world compression algorithms sometimes producing unexpectedly large files? Lossless compression is not magic. It just gives the common patterns a short notation, compensating by the less common patterns ending up with a longer notation. By that logic, all lossless compression algorithms must sometimes give you a larger file back. A real world example of that is for instance giving a file containing 'a' and a line feed to gzip (2 bytes), it subsequently returns a 30 byte file. In general, compression tools do not break even for very small files.

My question is: Are some compression utilities bloating out larger files by some significant amount? (While "Give this file to 7z and watch you harddrive fail!" is cool, things like "This 4kb file will grow to 6kb." are also good.)

I can see a reason why such behaviour might not exist. If you for instance always put an extra bit to the output telling if the file is actually compressed, or just the original file in the cases where the compression fails, your output can never be worse than the original file plus 1 bit. I am however not sure if any such protection against unexpected large files is used.
If you take vanilla RLE in bitmap which does not have any consecutive runs it will increase file size two times. It is apparently very rarely used fact that BMP, TIFF and PCX allows compression, (not all applications supporting these formats even implement RLE scheme). This is very pathological case and since it mostly increase file size it is abandoned.

Normal compression algorithms include information of failure, so instead of huge increase you can expect several bytes per chunk increase. In those that do not check there are three methods of checking how far we can increase file: take already compressed file, take encrypted file or find pathological cases from algorithm.

I have generated $256 \text{ bytes}$ file with consecutive numbers.
Compressed as 7z LZMA: $349 \text{ bytes}$, LZMA2:$356 \text{ bytes}$, Deflate or Deflate64: $400 \text{ bytes}$, bz2: $388 \text{ bytes}$, PPMd: $421 \text{ bytes}$ so not that cool.