My favorite modes were one shot kills with knives or slappers only, power weapons with health cranked up, or anything involving prox mines :>
I haven't played it for years now, and I'm not sure how easy it is to get N64 consoles now, but if you want something similar, TimeSplitters for the Gamecube had very similar gameplay (and a lot more options, including bots and fully customisable loadouts).