Flipper Robot. This is a 150g combat robot. I'm attaching the .STEP file as well for those who want to edit.

Very simple build that doesn't require many extra tools. Wedges can be printed or cut out of a sturdy material. 0.5mm Titanium is ideal. But Plexi/Acrylic also work as well. Printed wedges work fine if you're just flipping things around the house. There are two styles of top plates also, flat plate version or thicker angled prints

Assembly tricks: I used a lighter and heated the nails when inserting them into the printed arms. This creates a tight fit and keeps them from backing out. Otherwise a drop of superglue keeps them in the arms. The holes in the body and the hole in the lifter linkage should a loose fit for the nails so they can rotate freely. The nail spacers are put on the nail to keep the servo linkage from moving too much laterally on the nail.

I use a paper clip to attach the flipper to the servo arm and cut off the excess after its bent.

The lego hub has tolerances to printed easily on my printer and be a snug fit, but attaching a tighter tolerance version incase you need it.

You can use #4 Plastite screws for everything (to save on buying parts). But I use #3 for the top brace and top panels and #4s to attach the wedges to the arms.

BOM:

Links here: https://docs.google.com/spreadsheets/d/1HqPwgTid8flR8bDFijHdza18m8T-cTUwRuQyM6YLlmM/edit#gid=1028422378

Hardware:
1qty 2" Brad Nail
2qty 3/4" or 1" Brad Nail
Small Zip Ties
Paper Clip
HotGlue/Superglue
4-20 Plastite Screws
3-24 Plastite Screws
Wheels: Lego 24x14 Tire

Electronics:

Flipper Servo: KST DS215MG V3

Here are other variations to look for that will also work. KST X12-508 or Corona DS929HV for a cheaper alternative.

Drive Motors: N20 Micro Gearmotor 30:1 or 1000rpm

ESC: Malenki Nano

Battery: Nano-tech 300mah 2S Lipo Pack

Note: Any micro servo will work, but you'll be limited on flipping power. For that reason, I prefer the servos linked above, but you can build with a cheaper servo to test first.

You can buy these wheels to save weight if needed. Although the lego wheels work great and are much cheaper

SC-2110p ProComp