I've been using MODPlug for years. Only recently have I started using FL, which is quite good for sequencing some loops and such. MODPlug works well for in-depth stuff, and if you're into making glitch electronica or Drill N' Bass akin to Aphex Twin, it'll blow your mind. For pretty much everything minus making, well, rock, it's good. Even then, you could program some wicked basslines and drums in it and then just record some guitar through your line-in. Buzz is alright, not quite my thing though, as I'm more of the "sampler" type. I love sampling things to make instruments - speaking of which, everybody using MODPlug should take it upon themselves to write a song using only PSDs (Photoshop Files), PNGs (PNG Images), DLLs, and EXEs... and WADs, if you want.
