I've been playing these for as long as I can remember.
Rise of the Triad was originally supposed to be the sequel to Wolf3D. The developers of incredible power clearly had fun finishing this game off.
Day of the Tentacle is my favorite SCUMM engine game. The humor, the story, and the puzzles are all very enjoyable.
Jedi Knight was the first game I ever tried modding. The COG scripting engine was pretty easy to learn/work with. So many memories playing multiplayer on the MSN gaming zone after loading up mods/levels from
www.massassi.net. Fun fact: I played with my current gamertag on the MSN gaming zone.
Tyrian is one of two SHMUPS I started with (the other being Raptor: Call of the Shadows). I had access to Raptor first, but Tyrian just felt like it had so much more to offer. The jukebox/soundtrack is hard to beat. I still listen to it to this day on occasion. The story is great, and the devs definitely had fun with the story. The weapons/upgrades are plentiful and fun to experiment with... what other game lets you pilot a carrot shooting bananas? This one is actually currently free to play off GoG - I highly recommend it!