I have several favorites from seed catalogs: "Gee, that's pretty!". Delphiniums, Salvia, Columbines, Snapgragons and Penstemon.
But thesmart aswer would be "slug-resistant plants!" I fed hundreds of delph seedlings to slugs before i got one adult, which now blooms beatifully (I think "Pacific Giant").
This year I got several trays of Salvias to live past the damping-off stage, and many have gone into the gorund where they seem to be stalled.
Columbines & Snapdragons sprouted, but i ran out of space in my beds before they seemed stridy enoguh to put out.
I WS ed several Penstemon varieties - my first year WSing. I said "0% germination" and set the tubs aside until I had time to dump the soil and wash the pots. MONTHS later i was ready to dump them and I HAPPENED to look closely at the funny-colored Perlite, and lo and behold, those were teeny-tiny penstemon sprouts. Another month later, aned they are still tinyy.
Corey