Some of the best systemless RPG supplements ever published were from the CityBooks line of releases from Flying Buffalo. As for traps, few were as entertaining as the Grimtooth's Traps Collection.
You can get CityBooks I-III, Grimtooth's Traps I and II as well as a book on unique magic items in the Catalyst Bundle of Holding for just 7.95. That is a bargain and a half.
If you step up to about 23 bucks, you add the following:
- CityBooks IV-VII: Four more sets of people and places you can easily drop into any city adventure -- IV: On the Road, V: Sideshow, VI: Up Town, and VII: King's River Bridge.
- Grimtooth's Traps 3-4: Titled Fore and Ate (don't ask us why), these two books give you hundreds more traps to waylay dungeon delvers.
- NEW IN THIS REVIVAL! City of the Gods Map Pack: The wondrous place built by all the pantheons of Earth after they left this world behind.
- Mercenaries Spies & Private Eyes: Michael Stackpole's classic action/espionage RPG inspired by Tunnels & Trolls. Includes the Adventure of the Jade Jaguar solo adventure. (Both were also part of our September 2018 Tunnels & Trolls Bundle.)
- NEW! Mugshots No. 1 - The Case of the Pacific Clipper: A high-flying pulp-era solo adventure for MSPE written by Dungeons & Dragons co-designer Dave Arneson.
Personally, I love Mercenaries Spies & Private Eyes (just got my Kickstarter hardcover of the rules delivered yesterday). All that said, the seven CityBooks are worth the extra money on their own.
The usual 10% donation from Bundle of Holding is being given to Rick Loomis to help offset expenses related to his current cancer treatment.