SketchUp was my introduction to 3D, it's perfect for architectural modelling and by far the easiest modelling software to grasp. It's also great fun, it makes you want to wake the neighbors and get them to come and have a look :)   Empowered by SketchUp, I tried Spatch and then HamaPatch and made lots of poser props with those.

Then I switched to Wings3D and I've used it for years. It took me quite a while to settle into it but I'm glad I persevered, now I really love the efficiency of its 'bare bones', no-frills approach, but it can appear bleak and unwelcoming to newcomers. Once you 'get' the big picture of how wings works it is remarkably simple and surprisingly powerful and its UVmapping tools are excellent..

Just recently I decided to look higher up the food chain and I tried Rhino (didn't like the interface and decided poly modelling for poser wouldn't bring out the best in it), then Hex (didn't fall in love) and Modo. I had pretty much decided Modo was the ticket and then this Hex deal happened so I'm immersing myself in Hex for a bit. Might still spring for Modo though.

It's hard to switch modellers though, it's a complex, long-term relationship you're forging and you've really got to invest a lot of time and effort in getting the right fit.