Actually for my personal todos I just use a page of paper. I don't carry it around but sometimes I copy some tasks on a paper snippet and put it into my pocket. The very nice thing about the paper list is that it has a limit. So I don't end up having more todos than I can handle.
However for work I like Asana. Paper would be too impractical...
However for work I like Asana. Paper would be too impractical...