My earliest mixes put bass off to the left—sometimes 100% hard-panned—but these days, unless I'm trying to replicate an on-stage lineup for a live or live-in-studio performance, bass is strictly center. It sounds odd to me otherwise. I don't think I've ever tried drums off to one side, but I might given a compelling reason (like the aforementioned staging-matching). Usually, it's kick and snare center, overheads panned audience perspective to varying degrees depending on micing technique, and any other spot mics panned to match audience perspective. Aside from panning for effect (word painting, etc.), lead vocals go to the center, often with backup vocals flanking at either side to varying degrees. If there are multiple simultaneous lead vocals (duet, trio, trading fours, etc.), I'll pan them just off center (with one dead center if an odd grouping). For individually mic'd vocal ensembles, I usually pan according to standing order, audience perspective; width will depend on the size of the group, among other factors.Having said that, it has become quite normal to place certain elements in the centre of the stereo image, such as vocals, drums and bass. It always had a lot to do with compatibility for radio play in mono etc.
To get back to the OP, I hardly ever pan reverb anything but straight-up-the-middle. If it's a stereo reverb, it might be hard-panned or narrower, possibly with channels reversed. Delay will depend on numerous factors, but I don't think I favor one side over another. Other effects generally get applied directly to the source, wherever it is panned.