Is it worth buying a controller for PC?

Yes. Some games are just better suited to controllers.

Well, if you're considering, what games would you play with it?

It's always best to have as much stuff as possible. :D

Certainly I'd say it's best to have one, some games are quite cumbersome if you use keyboard. I know people do play Dirt, F1 etc with a keyboard, but they are crazy.

Favourite pad for me is the X360 wireless, but others are a lot cheaper.

No, not at all. You can play just about anything at least as well with keyboard and mouse. Controllers are just for casual players who want to relax while playing.

If you are going to play FPS games on it, it's a big no no. Although if you are going to play platformers or racing games then you should definetely go for it.

Any platformers or Port from consoles normally is better played with a controller :P

If a game was made with a controller in mind, it might be better using one than a keyboard/mouse combo. I have an X360 Wireless as well but I haven't used it in a while. Too much FM 2013 I think... :)

For games other than FPS or RTS, absolutely. You can always use a PS3 controller, though. I have a wired 360 controller for platformers, sandbox games, and racing games. Works like a charm.

you can buy one of those generic controllers and when a game doesnt recognize it you will need to use "emulators" like joy2ket,xpadder,xbox360emu,etc to make it work for those games if you are in trouble with money but yeah you need a controller for most ports unless you are fine playing with k+m

Why would you want that ... peasant tool... for you glorious PC ?

some games are better with controllers, platformers or racing games and some rpgs come good with controllers, but fps games are a big no, there is a reason consoles include auto aim on fps, mouses are far better for the job, also the same for third person shooters etc.

Generally, no. They're rarely of any use, only crap console ports and platformers come to mind. But then, those things are generally not worth playing anyway.

Though I like precision of mouse+keyboard in FPS, I prefer playing with controller just to give my hands some exercises they're not used to (playing with analog controller might be a challenge at first, especially for your thumbs ;) ). Plus it is more ergonomic to play with controller, which is vital if you're a musician or your work is tied with a lot of typing. I like playing FPS and simulators with it, as well as many other games supporting it. I've bought a controller about half a year ago and I think it's one of my best buys ever :) BUT there are some games I hate playing with analog controller (like Super Meat Boy), so I play either with keyboard or with... er... that crossy thing on it like on the old NES controllers I've played in my childhood. If you're dubious, well, give it a try. And if you don't like, you may always gift it to a friend on his/her birthday or just sell it. Or you might utilize it to play local co-op with friends ;)