A lot of Team Fortress 2's particles and effects changed throughout development. Some used Half-Life 2 particles (blood), some modified Half-Life 2 particles (explosions) whereas others were created from the ground up (Teleporter/Muzzleflashes/Minigun Casings). The Beta Lighting was also very different, resembling J.C. Leyendecker's work more than the final game.
Add Thirdperson Beta Minigun MuzzleflashesDone! Add Sentry & Grenade/Stickybomb Launcher MuzzleflashesDone! Add Beta ExplosionsDone! Add Beta Minigun CasingsDone! Add the Beta Player LightingDone! Add Beta Flamethrower FlamesDone! Add Beta Cloak EffectsDone! Add Beta Grenade Launcher ParticlesDone! Add Beta Concrete DecalsDone! Add HL2-Style Blood Impact EffectsDone! Add Beta Rocket TrailsDone! Add Beta-Style Teleporter EffectsDone!