Science Fiction - Phule's Company by Robert Asprin.
Fantasy - Her Majesty's Wizard, and The Warlock in Spite of Himself, both by Christopher Stasheff. The Landover series is well done as well, though I found the sequels less interesting than the first book.
I keep wanting to read through The Culture books, moreso because of their ship names than anything else. Some of these are brilliantly sarcastic. http://en.wikipedia.org/wiki/List_of_spacecraft_in_the_Culture_series
If you want cyberpunk, look into Shadowrun. A lot of the books are only loosely related to each other, with various different authors, but my favourites are Crossroads and Heads or Tails.
Lastly, the DOOM books. Yes, the books written to follow the plotline of the original DOOM and DOOM II games. I believe they were marketed as a "Space Opera", whatever the hell that means, but the first two are excellent. The third is alright, and the fourth starts going entirely off the rails in terms of metaphysicality. Is that a word? It is now. Metaphysical in and of itself describes a lot of the later plot fairly well, and some of the early bits. They did a surprisingly good job filling in characters aside from just The Doom Guy (Cpl. Flynn Taggart, now), and still has one of my favourite fictional female leads (PFC Arlene Sanders). Not the DOOM3 novelization - Knee Deep In The Dead, Hell on Earth, Infernal Sky, and End Game.