Budget conscious Warhammer 40k players or people who love dabbling in different wargames should check out Brassbound: Adamantine Dawn, an indie science fiction wargame that can be played with any 15mm scale miniatures, including ones you cobble together from Lego. The free rulebook even ends with instructions to build your own tiny-scale Lego tanks, troops, and war-mechs, and it's accompanied by a parts list that makes it simple to order all the bricks you need from Lego marketplace BrickLink.
Many wargame designers have looked at a table laid out with Warhammer 40k minis and wondered "what if all this was Lego?", resulting in games like BrikWars and Mobile Frame Zero. As anyone who has bought an expensive Lego set will expect, this isn't necessarily a ticket to a cheaper wargame - a lot comes down to which parts you use and how big the models are.
I'm happy to report that the suggested starter set for Brassbound is very affordable, at least in the UK. The Itch.io page for the game contains a free downloadable file for the rules, and a list of Lego parts needed to make the starter set. You can import this list into your account on Lego marketplace BrickLink, which can pair you with a retailer with the parts on offer: I found a UK seller that could provide everything to make two small starter forces for under $20.
I haven't had a chance to test Brassbound yet, but I've given the rules a read. It's very committed to the Lego theme, with everything measured in standard bricks, even the recommended size of the game table. It seems like a fairly light ruleset, but not a flimsy one, and it takes advantage of the Lego scenery to include rules for destructible terrain, something I always approve of.
The overlap between people who collect Warhammer 40k factions and people who collect Lego is a pretty big one, and if you are in the centre of that Venn diagram you can likely try out this game at no expense. A lot of the biggest Lego sets are architecture kits that would actually be the perfect scale for Brassbound - if you have a Lego football stadium, Hogwarts castle, or Taj Mahal, you could easily turn it into a battleground for this wargame.
If you've ever played wargames with toys, you're Wargamer's kind of person. We'd love to meet you - come and say hi in the official Wargamer Discord community!
If you prefer historical wargames to sci-fi, make sure you check out this excellent Lego Bolt Action game - it's brick blasting carnage!