well i recently completed an assessment for a fairly well-known games company, in the uk.
exam was pretty easy multiple choice, simple coding, and maths.
good few questions related to and,xor, or, ‘ing binary and hex numbers.
simple questions like multiply matrices, questions about sampling rate of cd audio, compressions, xbox live\hardware, adsl\modem, bresenham algorithm, fix and analyse code ( Big oh notation).
write a bit of code.
all in all not bad, you typically have to hit a pass rate in all areas to be interviewed.. i dont think the pass rate though is the same for each area, maths\coding i think are higher (makes sense i suspose).