I use a Gralab 450 for my enlarger timing, and I have two Gralab 300's mounted strategically, hung on the wall. One is within arms reach of my developing tray, the other next to my Jobo CPP-2.
Before I got the Gralabs, I used a variety of inexpensive mechanical or digital kitchen timers of the sort that others have mentioned. I found that the mechanical ones that you set by turning a dial are easiest to set quickly, but most of them can only be set to one minute intervals. The digital ones require you to push a button repeatedly to set the time.
There are some digital ones that count up just by hitting a single button. Those are very convenient because you don't have to set a time, just start the count up and keep an eye on it.
I have a hard time seeing most of the digital ones with LCD in the dark. Some have higher contrast LCD screens. If positioned so your safelight reflects on them, they are easy enough to read.
Wall mounting a timer makes it easier to use. I have dropped a couple of the small handheld kitchen style timers in the dev or fix tray while setting them. Some of them survived that, others did not.