Dahlia

I think that is a dipladinia,the mandaville has more textured leaves.Here's a mandaville from google,and this is exactly what mine looks like,very textured leaves. https://www.google.com/search?q=mandevilla+flowers&espv=2&biw=1600&bih=775&tbm=isch&imgil=1_FAOEfkU-WCyM%253A%253BRfh2MGKRjnbeLM%253Bhttp%25253A%25252F%25252Fwww.hgtv.com%25252Fgarden-galleries%25252Fflowers-for-your-greenhouse%25252Fpictures%25252F&source=iu&pf=m&fir=1_FAOEfkU-WCyM%253A%252CRfh2MGKRjnbeLM%252C_&usg=__3bRC2Q9hwiSYVog2ecbxcmprmrI%3D&ved=0CEoQyjc&ei=_kwfVJKSLsizogTQ04GABA#facrc=_&imgdii=_&imgrc=F3sad-zjywQr6M%253A%3BuVxTBP7YY-92bM%3Bhttp%253A%252F%252Fcdn.hgtvgardens.com%252Fdims4%252FGRDN%252Fe052727%252F2147483647%252Fresize%252F616x%252Fquality%252F90%252F%253Furl%253Dhttp%25253A%25252F%25252Fcdn.hgtvgardens.com%25252F64%25252F93%25252Fda38f2a047bdbc64eb2ce9b36a56%25252Fmandevilla-flowering-vine%3Bhttp%253A%252F%252Fwww.hgtvgardens.com%252Fflowers-and-plants%252Fflower-of-the-day-mandevilla%3B616%3B821 Sorry you'll have to copy and paste. Kathi

Shame you guys missed that flower, its definatly an orchid cactus, probably an epiphyllum as mentioned. Filtered light and regular feeding will get you more flowers. Its a nice lookin plant :D

Nope. I've ran a bunch of different flowers through my head. It isn't centranthus ruber, rock cress, soapwort, yarrow, pulmonaria, mountain laurel, dame's rocket or kalanchoe. Although all of those do have an inflorescence of several tiny pink flowers and they come in different plant forms so you might find you like one of those just as much if not more. Still stumped by this picture though. Notable features: very thin, needlelike leaves, five semi-fused petals, and a pink pistil in the middle of the very red cup. Yep... still stumped.