Frell (which originated on the incredibly awesome sci-fi show Farscape) is easily the greatest curseword of all time. Due to the similarity between it and hell, it can be used in any situation that the latter can, and, due to its meaning, can be used in any situation where the more known "f word" would be appropriate. It has unmatched versatility, and it references an awesome TV show that not enough people know of. What need would anyone have for another curseword?

Personally, I'm not a big fan of cursing, as it almost never actually adds anything to a conversation, and I feel that given how often most people curse, the words lose their impact. There's nothing shocking about cursewords when people use them all the time, so what's the point?