In the process of querying, I put together a spreadsheet of over 150 agents who represent fantasy (sorry, writers of other genres, but this was originally made for me, although sci-fi will likely find a worthwhile amount of overlap). Since I put so much effort into it, I figured I might as well allow other to reap the benefits as well, so I made a new version of it on Google Sheets for anyone to see.
(Please let me know if you have problems viewing it, because I don't tend use my Google Drive for much more than a source for storing story backups.)
In it, you'll find agents listed by agency, with such things included as their email, website, Twitter handle, and submission requirements. Most agents are based in the US, although I believe a couple Canadian and British agents slipped in. I also set up a chart that you can use to keep track of your requests vs rejections; all you have to do is enter the correct code in a specific column (P for a pending query, for instance, R for rejection, etc.), and the chart will do the rest. I also like to color-code mine so I can see at a quick glance whether I've queried an agent before. You can sort it in other ways, of course, although that might mess up the formulas on my chart, just be aware.
I got most, but not all, of my information from https://querytracker.net/. That's also the resource I use to estimate when I will hear back from an agent. For agents I have personally queried, I included the number of days it took for me to hear back, just as an extra piece of information to use.
Please keep in mind, I have not personally vetted these agents. I can make no claims as to the quality of these agents. Also, while it's a large list, it's certainly not all-encompassing. For instance, I left out agents whose only fantasy is urban fantasy, because that didn't apply to me. I'm sure there are agents I missed. New agents will pop up. Old agents will change careers or retire. I know there are a few agents on this list that don't pop up anymore, but I left them on just in case they return to the fold. Some agents may change agencies. I think they're all correct as I write this, but no guarantees.
This is also not an excuse to just spam out 100 queries. Do your research with all agents you submit to. Make sure they're right for you, read their website to make sure they're still with that agency and at that email, that the submission requirements haven't changed.
I hope some people can find this of use. Anyone feel free to download the spreadsheet for their own personal use. If someone wants to use it as a template for another genre, that is completely fine with me as well. And definitely use QueryTracker as a way to look up agents, both to find them, and to check if people have had good experiences with them. There was one agent I was going to add to my list, but I left him out after reading the QT comments that he was absolutely terrible.
(I think you can make an account on QT and probably do something similar to what I've done with my spreadsheet online, but I've never looked into it. I like my spreadsheet.)